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 $62.71   13.154%   $70.9589   $70.96   $70.95   $71.00  
  Purchase #2 $52.62   13.546%   $59.7479   $59.75   $59.75   $59.70  
  Purchase #3 $203.46   10.538%   $224.9006   $224.90   $224.90   $224.90  
  Purchase #4 $214.64   10.779%   $237.776   $237.78   $237.80   $237.80  
  Purchase #5 $115.73   7.210%   $124.0741   $124.07   $124.05   $124.10  
  Purchase #6 $194.39   12.637%   $218.9551   $218.96   $218.95   $219.00  
  Purchase #7 $101.41   13.869%   $115.4746   $115.47   $115.45   $115.50  
  7 purchase totals = $944.96       $1,051.8872   $1,051.89   $1,051.85   $1,052.00