Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $216.63   10.164%   $238.6483   $238.65   $238.65   $238.60  
  Purchase #2 $111.54   6.343%   $118.615   $118.62   $118.60   $118.60  
  Purchase #3 $147.86   11.525%   $164.9009   $164.90   $164.90   $164.90  
  Purchase #4 $94.93   7.551%   $102.0982   $102.10   $102.10   $102.10  
  Purchase #5 $137.64   10.143%   $151.6008   $151.60   $151.60   $151.60  
  Purchase #6 $234.86   12.789%   $264.8962   $264.90   $264.90   $264.90  
  Purchase #7 $170.45   13.809%   $193.9874   $193.99   $194.00   $194.00  
  7 purchase totals = $1,113.91       $1,234.7468   $1,234.76   $1,234.75   $1,234.70