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 $184.54   9.518%   $202.1045   $202.10   $202.10   $202.10  
  Purchase #2 $190.42   10.137%   $209.7229   $209.72   $209.70   $209.70  
  Purchase #3 $156.85   6.118%   $166.4461   $166.45   $166.45   $166.40  
  Purchase #4 $245.84   5.715%   $259.8898   $259.89   $259.90   $259.90  
  Purchase #5 $123.80   8.252%   $134.016   $134.02   $134.00   $134.00  
  Purchase #6 $7.37   7.470%   $7.9205   $7.92   $7.90   $7.90  
  Purchase #7 $162.61   4.252%   $169.5242   $169.52   $169.50   $169.50  
  7 purchase totals = $1,071.43       $1,149.6240   $1,149.62   $1,149.55   $1,149.50