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 $201.67   7.352%   $216.4968   $216.50   $216.50   $216.50  
  Purchase #2 $210.74   9.763%   $231.3145   $231.31   $231.30   $231.30  
  Purchase #3 $63.31   4.442%   $66.1222   $66.12   $66.10   $66.10  
  Purchase #4 $193.58   5.832%   $204.8696   $204.87   $204.85   $204.90  
  Purchase #5 $143.91   12.249%   $161.5375   $161.54   $161.55   $161.50  
  Purchase #6 $117.65   3.251%   $121.4748   $121.47   $121.45   $121.50  
  Purchase #7 $37.91   12.366%   $42.598   $42.60   $42.60   $42.60  
  7 purchase totals = $968.77       $1,044.4134   $1,044.41   $1,044.35   $1,044.40