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 $221.99   11.244%   $246.9506   $246.95   $246.95   $247.00  
  Purchase #2 $173.82   12.283%   $195.1703   $195.17   $195.15   $195.20  
  Purchase #3 $213.63   7.596%   $229.8573   $229.86   $229.85   $229.90  
  Purchase #4 $248.88   10.123%   $274.0741   $274.07   $274.05   $274.10  
  Purchase #5 $82.32   8.366%   $89.2069   $89.21   $89.20   $89.20  
  Purchase #6 $220.29   6.235%   $234.0251   $234.03   $234.05   $234.00  
  Purchase #7 $203.63   6.211%   $216.2775   $216.28   $216.30   $216.30  
  7 purchase totals = $1,364.56       $1,485.5618   $1,485.57   $1,485.55   $1,485.70