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 $75.26   9.831%   $82.6588   $82.66   $82.65   $82.70  
  Purchase #2 $119.92   12.300%   $134.6702   $134.67   $134.65   $134.70  
  Purchase #3 $243.69   9.636%   $267.172   $267.17   $267.15   $267.20  
  Purchase #4 $145.31   5.188%   $152.8487   $152.85   $152.85   $152.80  
  Purchase #5 $195.86   8.733%   $212.9645   $212.96   $212.95   $213.00  
  Purchase #6 $231.70   6.259%   $246.2021   $246.20   $246.20   $246.20  
  Purchase #7 $101.69   8.677%   $110.5136   $110.51   $110.50   $110.50  
  7 purchase totals = $1,113.43       $1,207.0299   $1,207.02   $1,206.95   $1,207.10