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 $59.88   6.324%   $63.6668   $63.67   $63.65   $63.70  
  Purchase #2 $170.30   11.787%   $190.3733   $190.37   $190.35   $190.40  
  Purchase #3 $195.60   13.218%   $221.4544   $221.45   $221.45   $221.50  
  Purchase #4 $90.82   12.669%   $102.326   $102.33   $102.35   $102.30  
  Purchase #5 $223.74   11.687%   $249.8885   $249.89   $249.90   $249.90  
  Purchase #6 $212.34   10.231%   $234.0645   $234.06   $234.05   $234.10  
  Purchase #7 $96.53   3.331%   $99.7454   $99.75   $99.75   $99.70  
  7 purchase totals = $1,049.21       $1,161.5189   $1,161.52   $1,161.50   $1,161.60