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 $179.77   8.617%   $195.2608   $195.26   $195.25   $195.30  
  Purchase #2 $90.89   7.784%   $97.9649   $97.96   $97.95   $98.00  
  Purchase #3 $244.56   8.501%   $265.35   $265.35   $265.35   $265.40  
  Purchase #4 $225.29   3.539%   $233.263   $233.26   $233.25   $233.30  
  Purchase #5 $183.66   9.765%   $201.5944   $201.59   $201.60   $201.60  
  Purchase #6 $241.67   10.447%   $266.9173   $266.92   $266.90   $266.90  
  Purchase #7 $243.62   9.777%   $267.4387   $267.44   $267.45   $267.40  
  7 purchase totals = $1,409.46       $1,527.7891   $1,527.78   $1,527.75   $1,527.90