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 $68.65   9.506%   $75.1759   $75.18   $75.20   $75.20  
  Purchase #2 $212.27   12.498%   $238.7995   $238.80   $238.80   $238.80  
  Purchase #3 $195.57   13.223%   $221.4302   $221.43   $221.45   $221.40  
  Purchase #4 $59.64   7.197%   $63.9323   $63.93   $63.95   $63.90  
  Purchase #5 $74.64   5.149%   $78.4832   $78.48   $78.50   $78.50  
  Purchase #6 $20.94   6.268%   $22.2525   $22.25   $22.25   $22.30  
  Purchase #7 $20.58   12.732%   $23.2002   $23.20   $23.20   $23.20  
  7 purchase totals = $652.29       $723.2738   $723.27   $723.35   $723.30