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 $218.32   7.547%   $234.7966   $234.80   $234.80   $234.80  
  Purchase #2 $200.38   4.407%   $209.2107   $209.21   $209.20   $209.20  
  Purchase #3 $182.50   9.570%   $199.9653   $199.97   $199.95   $200.00  
  Purchase #4 $23.28   9.487%   $25.4886   $25.49   $25.50   $25.50  
  Purchase #5 $154.30   13.622%   $175.3187   $175.32   $175.30   $175.30  
  Purchase #6 $58.66   10.589%   $64.8715   $64.87   $64.85   $64.90  
  Purchase #7 $137.30   4.508%   $143.4895   $143.49   $143.50   $143.50  
  7 purchase totals = $974.74       $1,053.1409   $1,053.15   $1,053.10   $1,053.20