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 $182.96   6.609%   $195.0518   $195.05   $195.05   $195.10  
  Purchase #2 $244.72   9.784%   $268.6634   $268.66   $268.65   $268.70  
  Purchase #3 $71.62   6.535%   $76.3004   $76.30   $76.30   $76.30  
  Purchase #4 $66.68   8.241%   $72.1751   $72.18   $72.20   $72.20  
  Purchase #5 $200.74   5.288%   $211.3551   $211.36   $211.35   $211.40  
  Purchase #6 $73.59   5.738%   $77.8126   $77.81   $77.80   $77.80  
  Purchase #7 $247.81   7.613%   $266.6758   $266.68   $266.70   $266.70  
  7 purchase totals = $1,088.12       $1,168.0342   $1,168.04   $1,168.05   $1,168.20