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 $217.31   5.687%   $229.6684   $229.67   $229.65   $229.70  
  Purchase #2 $220.27   9.699%   $241.634   $241.63   $241.65   $241.60  
  Purchase #3 $18.52   4.139%   $19.2865   $19.29   $19.30   $19.30  
  Purchase #4 $180.59   11.247%   $200.901   $200.90   $200.90   $200.90  
  Purchase #5 $244.51   12.837%   $275.8977   $275.90   $275.90   $275.90  
  Purchase #6 $13.64   4.543%   $14.2597   $14.26   $14.25   $14.30  
  Purchase #7 $75.40   7.816%   $81.2933   $81.29   $81.30   $81.30  
  7 purchase totals = $970.24       $1,062.9406   $1,062.94   $1,062.95   $1,063.00