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 $91.73   4.153%   $95.5395   $95.54   $95.55   $95.50  
  Purchase #2 $24.50   12.784%   $27.6321   $27.63   $27.65   $27.60  
  Purchase #3 $162.85   6.841%   $173.9906   $173.99   $174.00   $174.00  
  Purchase #4 $72.69   11.245%   $80.864   $80.86   $80.85   $80.90  
  Purchase #5 $132.80   12.492%   $149.3894   $149.39   $149.40   $149.40  
  Purchase #6 $150.46   5.826%   $159.2258   $159.23   $159.25   $159.20  
  Purchase #7 $242.46   9.719%   $266.0247   $266.02   $266.00   $266.00  
  7 purchase totals = $877.49       $952.6661   $952.66   $952.70   $952.60