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 $175.43   11.159%   $195.0062   $195.01   $195.00   $195.00  
  Purchase #2 $144.38   7.785%   $155.62   $155.62   $155.60   $155.60  
  Purchase #3 $12.76   11.441%   $14.2199   $14.22   $14.20   $14.20  
  Purchase #4 $161.39   5.562%   $170.3665   $170.37   $170.35   $170.40  
  Purchase #5 $83.64   5.162%   $87.9575   $87.96   $87.95   $88.00  
  Purchase #6 $165.28   9.497%   $180.9766   $180.98   $181.00   $181.00  
  Purchase #7 $206.45   5.216%   $217.2184   $217.22   $217.20   $217.20  
  7 purchase totals = $949.33       $1,021.3651   $1,021.38   $1,021.30   $1,021.40