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 $228.38   7.277%   $244.9992   $245.00   $245.00   $245.00  
  Purchase #2 $241.95   8.411%   $262.3004   $262.30   $262.30   $262.30  
  Purchase #3 $10.25   9.572%   $11.2311   $11.23   $11.25   $11.20  
  Purchase #4 $5.39   5.808%   $5.7031   $5.70   $5.70   $5.70  
  Purchase #5 $195.70   10.820%   $216.8747   $216.87   $216.85   $216.90  
  Purchase #6 $62.79   5.415%   $66.1901   $66.19   $66.20   $66.20  
  Purchase #7 $149.58   11.630%   $166.9762   $166.98   $167.00   $167.00  
  7 purchase totals = $894.04       $974.2748   $974.27   $974.30   $974.30