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 $245.97   7.593%   $264.6465   $264.65   $264.65   $264.60  
  Purchase #2 $185.79   10.338%   $204.997   $205.00   $205.00   $205.00  
  Purchase #3 $166.65   9.464%   $182.4218   $182.42   $182.40   $182.40  
  Purchase #4 $243.77   9.642%   $267.2743   $267.27   $267.25   $267.30  
  Purchase #5 $155.84   7.188%   $167.0418   $167.04   $167.05   $167.00  
  Purchase #6 $113.68   5.147%   $119.5311   $119.53   $119.55   $119.50  
  Purchase #7 $150.32   12.553%   $169.1897   $169.19   $169.20   $169.20  
  7 purchase totals = $1,262.02       $1,375.1022   $1,375.10   $1,375.10   $1,375.00