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 $85.32   13.752%   $97.0532   $97.05   $97.05   $97.10  
  Purchase #2 $51.35   8.173%   $55.5468   $55.55   $55.55   $55.50  
  Purchase #3 $184.96   10.258%   $203.9332   $203.93   $203.95   $203.90  
  Purchase #4 $64.88   7.707%   $69.8803   $69.88   $69.90   $69.90  
  Purchase #5 $175.30   7.311%   $188.1162   $188.12   $188.10   $188.10  
  Purchase #6 $217.50   5.746%   $229.9976   $230.00   $230.00   $230.00  
  Purchase #7 $184.67   8.300%   $199.9976   $200.00   $200.00   $200.00  
  7 purchase totals = $963.98       $1,044.5249   $1,044.53   $1,044.55   $1,044.50