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 $88.97   7.543%   $95.681   $95.68   $95.70   $95.70  
  Purchase #2 $245.65   4.666%   $257.112   $257.11   $257.10   $257.10  
  Purchase #3 $76.29   11.519%   $85.0778   $85.08   $85.10   $85.10  
  Purchase #4 $212.48   10.386%   $234.5482   $234.55   $234.55   $234.50  
  Purchase #5 $11.90   12.223%   $13.3545   $13.35   $13.35   $13.40  
  Purchase #6 $5.69   12.127%   $6.38   $6.38   $6.40   $6.40  
  Purchase #7 $37.96   9.826%   $41.6899   $41.69   $41.70   $41.70  
  7 purchase totals = $678.94       $733.8434   $733.84   $733.90   $733.90