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 $202.26   4.303%   $210.9632   $210.96   $210.95   $211.00  
  Purchase #2 $142.96   10.821%   $158.4297   $158.43   $158.45   $158.40  
  Purchase #3 $248.75   11.228%   $276.6797   $276.68   $276.70   $276.70  
  Purchase #4 $187.65   7.114%   $200.9994   $201.00   $201.00   $201.00  
  Purchase #5 $66.75   11.591%   $74.487   $74.49   $74.50   $74.50  
  Purchase #6 $150.61   6.868%   $160.9539   $160.95   $160.95   $161.00  
  Purchase #7 $67.25   4.132%   $70.0288   $70.03   $70.05   $70.00  
  7 purchase totals = $1,066.23       $1,152.5417   $1,152.54   $1,152.60   $1,152.60