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 $53.82   13.590%   $61.1341   $61.13   $61.15   $61.10  
  Purchase #2 $235.97   3.830%   $245.0077   $245.01   $245.00   $245.00  
  Purchase #3 $141.82   11.618%   $158.2966   $158.30   $158.30   $158.30  
  Purchase #4 $184.46   10.169%   $203.2177   $203.22   $203.20   $203.20  
  Purchase #5 $154.87   7.795%   $166.9421   $166.94   $166.95   $166.90  
  Purchase #6 $192.74   7.293%   $206.7965   $206.80   $206.80   $206.80  
  Purchase #7 $149.78   5.166%   $157.5176   $157.52   $157.50   $157.50  
  7 purchase totals = $1,113.46       $1,198.9123   $1,198.92   $1,198.90   $1,198.80