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 $244.37   9.493%   $267.568   $267.57   $267.55   $267.60  
  Purchase #2 $72.83   13.389%   $82.5812   $82.58   $82.60   $82.60  
  Purchase #3 $143.98   6.566%   $153.4337   $153.43   $153.45   $153.40  
  Purchase #4 $235.78   7.204%   $252.7656   $252.77   $252.75   $252.80  
  Purchase #5 $122.48   8.603%   $133.017   $133.02   $133.00   $133.00  
  Purchase #6 $73.30   4.393%   $76.5201   $76.52   $76.50   $76.50  
  Purchase #7 $60.77   8.461%   $65.9117   $65.91   $65.90   $65.90  
  7 purchase totals = $953.51       $1,031.7973   $1,031.80   $1,031.75   $1,031.80