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 $61.59   8.780%   $66.9976   $67.00   $67.00   $67.00  
  Purchase #2 $153.96   10.548%   $170.1997   $170.20   $170.20   $170.20  
  Purchase #3 $149.29   3.701%   $154.8152   $154.82   $154.80   $154.80  
  Purchase #4 $105.56   6.430%   $112.3475   $112.35   $112.35   $112.30  
  Purchase #5 $76.76   3.514%   $79.4573   $79.46   $79.45   $79.50  
  Purchase #6 $102.81   10.549%   $113.6554   $113.66   $113.65   $113.70  
  Purchase #7 $45.31   7.611%   $48.7585   $48.76   $48.75   $48.80  
  7 purchase totals = $695.28       $746.2312   $746.25   $746.20   $746.30