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 $204.41   8.460%   $221.7031   $221.70   $221.70   $221.70  
  Purchase #2 $210.75   10.219%   $232.2865   $232.29   $232.30   $232.30  
  Purchase #3 $243.42   7.839%   $262.5017   $262.50   $262.50   $262.50  
  Purchase #4 $77.79   13.566%   $88.343   $88.34   $88.35   $88.30  
  Purchase #5 $175.31   5.329%   $184.6523   $184.65   $184.65   $184.70  
  Purchase #6 $102.49   6.610%   $109.2646   $109.26   $109.25   $109.30  
  Purchase #7 $47.60   11.696%   $53.1673   $53.17   $53.15   $53.20  
  7 purchase totals = $1,061.77       $1,151.9185   $1,151.91   $1,151.90   $1,152.00