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 $115.38   9.172%   $125.9627   $125.96   $125.95   $126.00  
  Purchase #2 $66.84   8.230%   $72.3409   $72.34   $72.35   $72.30  
  Purchase #3 $229.52   9.418%   $251.1362   $251.14   $251.15   $251.10  
  Purchase #4 $212.74   9.412%   $232.7631   $232.76   $232.75   $232.80  
  Purchase #5 $159.54   10.302%   $175.9758   $175.98   $176.00   $176.00  
  Purchase #6 $101.35   8.805%   $110.2739   $110.27   $110.25   $110.30  
  Purchase #7 $69.50   9.319%   $75.9767   $75.98   $76.00   $76.00  
  7 purchase totals = $954.87       $1,044.4293   $1,044.43   $1,044.45   $1,044.50