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 $212.61   7.350%   $228.2368   $228.24   $228.25   $228.20  
  Purchase #2 $199.97   4.835%   $209.6385   $209.64   $209.65   $209.60  
  Purchase #3 $25.71   7.497%   $27.6375   $27.64   $27.65   $27.60  
  Purchase #4 $77.92   7.337%   $83.637   $83.64   $83.65   $83.60  
  Purchase #5 $68.72   10.734%   $76.0964   $76.10   $76.10   $76.10  
  Purchase #6 $194.26   12.737%   $219.0029   $219.00   $219.00   $219.00  
  Purchase #7 $198.76   13.673%   $225.9365   $225.94   $225.95   $225.90  
  7 purchase totals = $977.95       $1,070.1856   $1,070.20   $1,070.25   $1,070.00