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 $88.81   6.682%   $94.7443   $94.74   $94.75   $94.70  
  Purchase #2 $69.74   7.559%   $75.0116   $75.01   $75.00   $75.00  
  Purchase #3 $57.74   9.709%   $63.346   $63.35   $63.35   $63.30  
  Purchase #4 $210.75   6.412%   $224.2633   $224.26   $224.25   $224.30  
  Purchase #5 $48.96   6.381%   $52.0841   $52.08   $52.10   $52.10  
  Purchase #6 $215.45   3.562%   $223.1243   $223.12   $223.10   $223.10  
  Purchase #7 $156.67   4.868%   $164.2967   $164.30   $164.30   $164.30  
  7 purchase totals = $848.12       $896.8703   $896.86   $896.85   $896.80