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 $83.47   13.404%   $94.6583   $94.66   $94.65   $94.70  
  Purchase #2 $130.45   9.775%   $143.2015   $143.20   $143.20   $143.20  
  Purchase #3 $180.94   3.556%   $187.3742   $187.37   $187.35   $187.40  
  Purchase #4 $230.80   6.145%   $244.9827   $244.98   $245.00   $245.00  
  Purchase #5 $121.44   8.814%   $132.1437   $132.14   $132.15   $132.10  
  Purchase #6 $238.73   11.775%   $266.8405   $266.84   $266.85   $266.80  
  Purchase #7 $112.92   12.463%   $126.9932   $126.99   $127.00   $127.00  
  7 purchase totals = $1,098.75       $1,196.1941   $1,196.18   $1,196.20   $1,196.20