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 $162.39   8.463%   $176.1331   $176.13   $176.15   $176.10  
  Purchase #2 $118.51   6.792%   $126.5592   $126.56   $126.55   $126.60  
  Purchase #3 $236.59   7.330%   $253.932   $253.93   $253.95   $253.90  
  Purchase #4 $98.41   10.319%   $108.5649   $108.56   $108.55   $108.60  
  Purchase #5 $169.45   9.554%   $185.6393   $185.64   $185.65   $185.60  
  Purchase #6 $10.42   6.414%   $11.0883   $11.09   $11.10   $11.10  
  Purchase #7 $236.94   6.170%   $251.5592   $251.56   $251.55   $251.60  
  7 purchase totals = $1,032.71       $1,113.4760   $1,113.47   $1,113.50   $1,113.50