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 $173.53   12.742%   $195.6412   $195.64   $195.65   $195.60  
  Purchase #2 $63.55   3.268%   $65.6268   $65.63   $65.65   $65.60  
  Purchase #3 $139.93   7.596%   $150.5591   $150.56   $150.55   $150.60  
  Purchase #4 $245.25   4.835%   $257.1078   $257.11   $257.10   $257.10  
  Purchase #5 $81.48   3.377%   $84.2316   $84.23   $84.25   $84.20  
  Purchase #6 $163.84   8.421%   $177.637   $177.64   $177.65   $177.60  
  Purchase #7 $76.90   7.205%   $82.4406   $82.44   $82.45   $82.40  
  7 purchase totals = $944.48       $1,013.2441   $1,013.25   $1,013.30   $1,013.10