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 $232.85   5.633%   $245.9664   $245.97   $245.95   $246.00  
  Purchase #2 $8.96   4.515%   $9.3645   $9.36   $9.35   $9.40  
  Purchase #3 $199.60   7.106%   $213.7836   $213.78   $213.80   $213.80  
  Purchase #4 $174.86   3.237%   $180.5202   $180.52   $180.50   $180.50  
  Purchase #5 $228.89   12.462%   $257.4143   $257.41   $257.40   $257.40  
  Purchase #6 $197.55   4.774%   $206.981   $206.98   $207.00   $207.00  
  Purchase #7 $209.40   5.851%   $221.652   $221.65   $221.65   $221.70  
  7 purchase totals = $1,252.11       $1,335.6820   $1,335.67   $1,335.65   $1,335.80