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 $57.79   7.297%   $62.0069   $62.01   $62.00   $62.00  
  Purchase #2 $100.48   5.229%   $105.7341   $105.73   $105.75   $105.70  
  Purchase #3 $50.49   12.462%   $56.7821   $56.78   $56.80   $56.80  
  Purchase #4 $175.98   4.283%   $183.5172   $183.52   $183.50   $183.50  
  Purchase #5 $120.83   7.414%   $129.7883   $129.79   $129.80   $129.80  
  Purchase #6 $242.65   6.505%   $258.4344   $258.43   $258.45   $258.40  
  Purchase #7 $237.46   12.385%   $266.8694   $266.87   $266.85   $266.90  
  7 purchase totals = $985.68       $1,063.1324   $1,063.13   $1,063.15   $1,063.10