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 $62.63   10.480%   $69.1936   $69.19   $69.20   $69.20  
  Purchase #2 $56.78   9.322%   $62.073   $62.07   $62.05   $62.10  
  Purchase #3 $32.29   4.110%   $33.6171   $33.62   $33.60   $33.60  
  Purchase #4 $8.30   5.487%   $8.7554   $8.76   $8.75   $8.80  
  Purchase #5 $49.42   6.280%   $52.5236   $52.52   $52.50   $52.50  
  Purchase #6 $241.59   4.637%   $252.7925   $252.79   $252.80   $252.80  
  Purchase #7 $195.72   10.214%   $215.7108   $215.71   $215.70   $215.70  
  7 purchase totals = $646.73       $694.6660   $694.66   $694.60   $694.70