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 $195.30   5.787%   $206.602   $206.60   $206.60   $206.60  
  Purchase #2 $56.99   13.664%   $64.7771   $64.78   $64.80   $64.80  
  Purchase #3 $82.30   4.385%   $85.9089   $85.91   $85.90   $85.90  
  Purchase #4 $203.26   8.169%   $219.8643   $219.86   $219.85   $219.90  
  Purchase #5 $186.35   8.740%   $202.637   $202.64   $202.65   $202.60  
  Purchase #6 $99.47   11.740%   $111.1478   $111.15   $111.15   $111.10  
  Purchase #7 $237.66   9.554%   $260.366   $260.37   $260.35   $260.40  
  7 purchase totals = $1,061.33       $1,151.3031   $1,151.31   $1,151.30   $1,151.30