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 $249.51   5.283%   $262.6916   $262.69   $262.70   $262.70  
  Purchase #2 $45.74   9.428%   $50.0524   $50.05   $50.05   $50.10  
  Purchase #3 $178.46   8.718%   $194.0181   $194.02   $194.00   $194.00  
  Purchase #4 $52.29   4.244%   $54.5092   $54.51   $54.50   $54.50  
  Purchase #5 $201.38   10.655%   $222.837   $222.84   $222.85   $222.80  
  Purchase #6 $208.51   8.120%   $225.441   $225.44   $225.45   $225.40  
  Purchase #7 $106.67   9.679%   $116.9946   $116.99   $117.00   $117.00  
  7 purchase totals = $1,042.56       $1,126.5439   $1,126.54   $1,126.55   $1,126.50