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 $182.68   7.215%   $195.8604   $195.86   $195.85   $195.90  
  Purchase #2 $228.49   7.565%   $245.7753   $245.78   $245.80   $245.80  
  Purchase #3 $5.67   7.751%   $6.1095   $6.11   $6.10   $6.10  
  Purchase #4 $110.88   6.185%   $117.7379   $117.74   $117.75   $117.70  
  Purchase #5 $20.63   12.248%   $23.1568   $23.16   $23.15   $23.20  
  Purchase #6 $170.65   9.315%   $186.546   $186.55   $186.55   $186.50  
  Purchase #7 $96.36   4.711%   $100.8995   $100.90   $100.90   $100.90  
  7 purchase totals = $815.36       $876.0854   $876.10   $876.10   $876.10