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 $223.49   4.590%   $233.7482   $233.75   $233.75   $233.70  
  Purchase #2 $124.75   6.358%   $132.6816   $132.68   $132.70   $132.70  
  Purchase #3 $218.77   11.521%   $243.9745   $243.97   $243.95   $244.00  
  Purchase #4 $97.47   11.478%   $108.6576   $108.66   $108.65   $108.70  
  Purchase #5 $192.56   6.330%   $204.749   $204.75   $204.75   $204.70  
  Purchase #6 $201.65   7.373%   $216.5177   $216.52   $216.50   $216.50  
  Purchase #7 $60.55   5.720%   $64.0135   $64.01   $64.00   $64.00  
  7 purchase totals = $1,119.24       $1,204.3421   $1,204.34   $1,204.30   $1,204.30