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 $58.99   3.417%   $61.0057   $61.01   $61.00   $61.00  
  Purchase #2 $238.57   9.569%   $261.3988   $261.40   $261.40   $261.40  
  Purchase #3 $21.35   12.494%   $24.0175   $24.02   $24.00   $24.00  
  Purchase #4 $209.26   12.286%   $234.9697   $234.97   $234.95   $235.00  
  Purchase #5 $214.52   6.794%   $229.0945   $229.09   $229.10   $229.10  
  Purchase #6 $206.74   4.485%   $216.0123   $216.01   $216.00   $216.00  
  Purchase #7 $226.43   8.566%   $245.826   $245.83   $245.85   $245.80  
  7 purchase totals = $1,175.86       $1,272.3245   $1,272.33   $1,272.30   $1,272.30