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 $87.81   5.549%   $92.6826   $92.68   $92.70   $92.70  
  Purchase #2 $90.85   12.269%   $101.9964   $102.00   $102.00   $102.00  
  Purchase #3 $65.96   4.311%   $68.8035   $68.80   $68.80   $68.80  
  Purchase #4 $78.85   10.474%   $87.1087   $87.11   $87.10   $87.10  
  Purchase #5 $102.74   7.709%   $110.6602   $110.66   $110.65   $110.70  
  Purchase #6 $89.46   6.260%   $95.0602   $95.06   $95.05   $95.10  
  Purchase #7 $195.36   3.637%   $202.4652   $202.47   $202.45   $202.50  
  7 purchase totals = $711.03       $758.7768   $758.78   $758.75   $758.90