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 $191.98   9.563%   $210.339   $210.34   $210.35   $210.30  
  Purchase #2 $202.30   5.761%   $213.9545   $213.95   $213.95   $214.00  
  Purchase #3 $129.35   5.213%   $136.093   $136.09   $136.10   $136.10  
  Purchase #4 $151.30   7.412%   $162.5144   $162.51   $162.50   $162.50  
  Purchase #5 $42.91   4.294%   $44.7526   $44.75   $44.75   $44.80  
  Purchase #6 $228.28   9.385%   $249.7041   $249.70   $249.70   $249.70  
  Purchase #7 $39.88   10.534%   $44.081   $44.08   $44.10   $44.10  
  7 purchase totals = $986.00       $1,061.4386   $1,061.42   $1,061.45   $1,061.50