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 $58.63   5.721%   $61.9842   $61.98   $62.00   $62.00  
  Purchase #2 $93.65   5.517%   $98.8167   $98.82   $98.80   $98.80  
  Purchase #3 $41.93   10.443%   $46.3087   $46.31   $46.30   $46.30  
  Purchase #4 $63.60   10.219%   $70.0993   $70.10   $70.10   $70.10  
  Purchase #5 $56.97   13.872%   $64.8729   $64.87   $64.85   $64.90  
  Purchase #6 $36.27   8.694%   $39.4233   $39.42   $39.40   $39.40  
  Purchase #7 $74.64   7.669%   $80.3641   $80.36   $80.35   $80.40  
  7 purchase totals = $425.69       $461.8692   $461.86   $461.80   $461.90