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 $55.46   12.172%   $62.2106   $62.21   $62.20   $62.20  
  Purchase #2 $243.97   8.495%   $264.6953   $264.70   $264.70   $264.70  
  Purchase #3 $126.83   4.861%   $132.9952   $133.00   $133.00   $133.00  
  Purchase #4 $40.82   3.428%   $42.2193   $42.22   $42.20   $42.20  
  Purchase #5 $240.70   10.603%   $266.2214   $266.22   $266.20   $266.20  
  Purchase #6 $14.28   9.497%   $15.6362   $15.64   $15.65   $15.60  
  Purchase #7 $244.85   9.244%   $267.4839   $267.48   $267.50   $267.50  
  7 purchase totals = $966.91       $1,051.4619   $1,051.47   $1,051.45   $1,051.40