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 $118.26   3.632%   $122.5552   $122.56   $122.55   $122.60  
  Purchase #2 $96.33   9.783%   $105.754   $105.75   $105.75   $105.80  
  Purchase #3 $121.79   8.519%   $132.1653   $132.17   $132.15   $132.20  
  Purchase #4 $88.71   8.713%   $96.4393   $96.44   $96.45   $96.40  
  Purchase #5 $184.90   5.799%   $195.6224   $195.62   $195.60   $195.60  
  Purchase #6 $68.68   7.237%   $73.6504   $73.65   $73.65   $73.70  
  Purchase #7 $191.70   4.494%   $200.315   $200.32   $200.30   $200.30  
  7 purchase totals = $870.37       $926.5016   $926.51   $926.45   $926.60