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 $114.38   3.639%   $118.5423   $118.54   $118.55   $118.50  
  Purchase #2 $87.55   11.433%   $97.5596   $97.56   $97.55   $97.60  
  Purchase #3 $82.95   13.173%   $93.877   $93.88   $93.90   $93.90  
  Purchase #4 $106.54   9.428%   $116.5846   $116.58   $116.60   $116.60  
  Purchase #5 $216.50   8.830%   $235.617   $235.62   $235.60   $235.60  
  Purchase #6 $191.37   5.539%   $201.97   $201.97   $201.95   $202.00  
  Purchase #7 $212.38   10.484%   $234.6459   $234.65   $234.65   $234.60  
  7 purchase totals = $1,011.67       $1,098.7964   $1,098.80   $1,098.80   $1,098.80