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 $56.89   9.498%   $62.2934   $62.29   $62.30   $62.30  
  Purchase #2 $49.85   4.214%   $51.9507   $51.95   $51.95   $52.00  
  Purchase #3 $97.31   6.852%   $103.9777   $103.98   $104.00   $104.00  
  Purchase #4 $142.65   7.476%   $153.3145   $153.31   $153.30   $153.30  
  Purchase #5 $61.40   11.421%   $68.4125   $68.41   $68.40   $68.40  
  Purchase #6 $135.61   5.235%   $142.7092   $142.71   $142.70   $142.70  
  Purchase #7 $218.70   10.836%   $242.3983   $242.40   $242.40   $242.40  
  7 purchase totals = $762.41       $825.0563   $825.05   $825.05   $825.10