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 $213.59   5.228%   $224.7565   $224.76   $224.75   $224.80  
  Purchase #2 $243.53   8.691%   $264.6952   $264.70   $264.70   $264.70  
  Purchase #3 $12.64   12.351%   $14.2012   $14.20   $14.20   $14.20  
  Purchase #4 $169.78   6.407%   $180.6578   $180.66   $180.65   $180.70  
  Purchase #5 $182.86   12.432%   $205.5932   $205.59   $205.60   $205.60  
  Purchase #6 $150.71   3.513%   $156.0044   $156.00   $156.00   $156.00  
  Purchase #7 $235.70   9.253%   $257.5093   $257.51   $257.50   $257.50  
  7 purchase totals = $1,208.81       $1,303.4176   $1,303.42   $1,303.40   $1,303.50