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 $59.76   4.182%   $62.2592   $62.26   $62.25   $62.30  
  Purchase #2 $198.91   13.860%   $226.4789   $226.48   $226.50   $226.50  
  Purchase #3 $91.61   10.814%   $101.5167   $101.52   $101.50   $101.50  
  Purchase #4 $204.85   11.483%   $228.3729   $228.37   $228.35   $228.40  
  Purchase #5 $243.64   5.344%   $256.6601   $256.66   $256.65   $256.70  
  Purchase #6 $79.40   11.601%   $88.6112   $88.61   $88.60   $88.60  
  Purchase #7 $84.36   4.851%   $88.4523   $88.45   $88.45   $88.50  
  7 purchase totals = $962.53       $1,052.3513   $1,052.35   $1,052.30   $1,052.50