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 $209.35   12.626%   $235.7825   $235.78   $235.80   $235.80  
  Purchase #2 $202.77   12.168%   $227.4431   $227.44   $227.45   $227.40  
  Purchase #3 $160.78   10.792%   $178.1314   $178.13   $178.15   $178.10  
  Purchase #4 $231.92   13.550%   $263.3452   $263.35   $263.35   $263.30  
  Purchase #5 $52.58   9.522%   $57.5867   $57.59   $57.60   $57.60  
  Purchase #6 $6.68   10.346%   $7.3711   $7.37   $7.35   $7.40  
  Purchase #7 $185.65   11.428%   $206.8661   $206.87   $206.85   $206.90  
  7 purchase totals = $1,049.73       $1,176.5261   $1,176.53   $1,176.55   $1,176.50