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 $233.57   5.302%   $245.9539   $245.95   $245.95   $246.00  
  Purchase #2 $177.94   3.118%   $183.4882   $183.49   $183.50   $183.50  
  Purchase #3 $49.67   5.300%   $52.3025   $52.30   $52.30   $52.30  
  Purchase #4 $214.96   13.471%   $243.9173   $243.92   $243.90   $243.90  
  Purchase #5 $235.59   13.535%   $267.4771   $267.48   $267.50   $267.50  
  Purchase #6 $40.61   6.211%   $43.1323   $43.13   $43.15   $43.10  
  Purchase #7 $210.61   7.468%   $226.3384   $226.34   $226.35   $226.30  
  7 purchase totals = $1,162.95       $1,262.6097   $1,262.61   $1,262.65   $1,262.60