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 $150.50   7.491%   $161.774   $161.77   $161.75   $161.80  
  Purchase #2 $219.55   8.133%   $237.406   $237.41   $237.40   $237.40  
  Purchase #3 $91.62   7.810%   $98.7755   $98.78   $98.80   $98.80  
  Purchase #4 $162.46   7.720%   $175.0019   $175.00   $175.00   $175.00  
  Purchase #5 $179.83   13.494%   $204.0963   $204.10   $204.10   $204.10  
  Purchase #6 $169.73   3.174%   $175.1172   $175.12   $175.10   $175.10  
  Purchase #7 $95.45   4.125%   $99.3873   $99.39   $99.40   $99.40  
  7 purchase totals = $1,069.14       $1,151.5582   $1,151.57   $1,151.55   $1,151.60