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 $60.49   3.572%   $62.6507   $62.65   $62.65   $62.70  
  Purchase #2 $20.44   3.479%   $21.1511   $21.15   $21.15   $21.20  
  Purchase #3 $238.92   5.254%   $251.4729   $251.47   $251.45   $251.50  
  Purchase #4 $54.89   7.265%   $58.8778   $58.88   $58.90   $58.90  
  Purchase #5 $148.27   5.634%   $156.6235   $156.62   $156.60   $156.60  
  Purchase #6 $61.33   9.276%   $67.019   $67.02   $67.00   $67.00  
  Purchase #7 $92.52   6.267%   $98.3182   $98.32   $98.30   $98.30  
  7 purchase totals = $676.86       $716.1132   $716.11   $716.05   $716.20