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 $90.44   6.275%   $96.1151   $96.12   $96.10   $96.10  
  Purchase #2 $237.43   12.457%   $267.0067   $267.01   $267.00   $267.00  
  Purchase #3 $227.89   7.395%   $244.7425   $244.74   $244.75   $244.70  
  Purchase #4 $87.98   3.258%   $90.8464   $90.85   $90.85   $90.80  
  Purchase #5 $41.76   4.473%   $43.6279   $43.63   $43.65   $43.60  
  Purchase #6 $102.96   10.862%   $114.1435   $114.14   $114.15   $114.10  
  Purchase #7 $240.73   11.338%   $268.024   $268.02   $268.00   $268.00  
  7 purchase totals = $1,029.19       $1,124.5061   $1,124.51   $1,124.50   $1,124.30