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 $215.80   9.694%   $236.7197   $236.72   $236.70   $236.70  
  Purchase #2 $53.99   10.147%   $59.4684   $59.47   $59.45   $59.50  
  Purchase #3 $159.75   3.612%   $165.5202   $165.52   $165.50   $165.50  
  Purchase #4 $84.27   9.503%   $92.2782   $92.28   $92.30   $92.30  
  Purchase #5 $148.73   8.266%   $161.024   $161.02   $161.00   $161.00  
  Purchase #6 $223.69   6.530%   $238.297   $238.30   $238.30   $238.30  
  Purchase #7 $175.70   6.566%   $187.2365   $187.24   $187.25   $187.20  
  7 purchase totals = $1,061.93       $1,140.5440   $1,140.55   $1,140.50   $1,140.50