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 $85.99   10.700%   $95.1909   $95.19   $95.20   $95.20  
  Purchase #2 $197.74   13.869%   $225.1646   $225.16   $225.15   $225.20  
  Purchase #3 $234.98   9.278%   $256.7814   $256.78   $256.80   $256.80  
  Purchase #4 $110.94   7.619%   $119.3925   $119.39   $119.40   $119.40  
  Purchase #5 $101.54   13.525%   $115.2733   $115.27   $115.25   $115.30  
  Purchase #6 $180.61   4.639%   $188.9885   $188.99   $189.00   $189.00  
  Purchase #7 $5.79   4.669%   $6.0603   $6.06   $6.05   $6.10  
  7 purchase totals = $917.59       $1,006.8515   $1,006.84   $1,006.85   $1,007.00