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 $61.95   4.452%   $64.708   $64.71   $64.70   $64.70  
  Purchase #2 $234.67   4.493%   $245.2137   $245.21   $245.20   $245.20  
  Purchase #3 $169.74   3.702%   $176.0238   $176.02   $176.00   $176.00  
  Purchase #4 $123.70   9.376%   $135.2981   $135.30   $135.30   $135.30  
  Purchase #5 $225.78   6.580%   $240.6363   $240.64   $240.65   $240.60  
  Purchase #6 $215.36   11.513%   $240.1544   $240.15   $240.15   $240.20  
  Purchase #7 $22.41   6.451%   $23.8557   $23.86   $23.85   $23.90  
  7 purchase totals = $1,053.61       $1,125.8900   $1,125.89   $1,125.85   $1,125.90