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 $197.94   3.363%   $204.5967   $204.60   $204.60   $204.60  
  Purchase #2 $215.59   4.196%   $224.6362   $224.64   $224.65   $224.60  
  Purchase #3 $215.67   10.619%   $238.572   $238.57   $238.55   $238.60  
  Purchase #4 $167.49   6.513%   $178.3986   $178.40   $178.40   $178.40  
  Purchase #5 $49.38   4.631%   $51.6668   $51.67   $51.65   $51.70  
  Purchase #6 $68.58   11.245%   $76.2918   $76.29   $76.30   $76.30  
  Purchase #7 $46.38   6.604%   $49.4429   $49.44   $49.45   $49.40  
  7 purchase totals = $961.03       $1,023.6050   $1,023.61   $1,023.60   $1,023.60