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 $89.25   7.839%   $96.2463   $96.25   $96.25   $96.20  
  Purchase #2 $108.79   10.132%   $119.8126   $119.81   $119.80   $119.80  
  Purchase #3 $226.85   7.812%   $244.5715   $244.57   $244.55   $244.60  
  Purchase #4 $78.96   5.660%   $83.4291   $83.43   $83.45   $83.40  
  Purchase #5 $238.63   11.118%   $265.1609   $265.16   $265.15   $265.20  
  Purchase #6 $242.75   10.368%   $267.9183   $267.92   $267.90   $267.90  
  Purchase #7 $94.71   13.817%   $107.7961   $107.80   $107.80   $107.80  
  7 purchase totals = $1,079.94       $1,184.9348   $1,184.94   $1,184.90   $1,184.90