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 $26.42   3.140%   $27.2496   $27.25   $27.25   $27.20  
  Purchase #2 $154.98   11.421%   $172.6803   $172.68   $172.70   $172.70  
  Purchase #3 $58.80   6.449%   $62.592   $62.59   $62.60   $62.60  
  Purchase #4 $246.56   10.192%   $271.6894   $271.69   $271.70   $271.70  
  Purchase #5 $182.67   7.135%   $195.7035   $195.70   $195.70   $195.70  
  Purchase #6 $165.95   4.314%   $173.1091   $173.11   $173.10   $173.10  
  Purchase #7 $185.25   11.740%   $206.9984   $207.00   $207.00   $207.00  
  7 purchase totals = $1,020.63       $1,110.0223   $1,110.02   $1,110.05   $1,110.00