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 $60.76   5.274%   $63.9645   $63.96   $63.95   $64.00  
  Purchase #2 $126.55   13.256%   $143.3255   $143.33   $143.35   $143.30  
  Purchase #3 $58.87   13.149%   $66.6108   $66.61   $66.60   $66.60  
  Purchase #4 $135.31   8.870%   $147.312   $147.31   $147.30   $147.30  
  Purchase #5 $212.39   7.791%   $228.9373   $228.94   $228.95   $228.90  
  Purchase #6 $242.31   7.640%   $260.8225   $260.82   $260.80   $260.80  
  Purchase #7 $237.61   9.683%   $260.6178   $260.62   $260.60   $260.60  
  7 purchase totals = $1,073.80       $1,171.5904   $1,171.59   $1,171.55   $1,171.50