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 $246.90   5.623%   $260.7832   $260.78   $260.80   $260.80  
  Purchase #2 $213.30   11.275%   $237.3496   $237.35   $237.35   $237.30  
  Purchase #3 $13.61   6.257%   $14.4616   $14.46   $14.45   $14.50  
  Purchase #4 $195.94   4.659%   $205.0688   $205.07   $205.05   $205.10  
  Purchase #5 $87.47   6.864%   $93.4739   $93.47   $93.45   $93.50  
  Purchase #6 $82.37   6.519%   $87.7397   $87.74   $87.75   $87.70  
  Purchase #7 $149.79   13.545%   $170.0791   $170.08   $170.10   $170.10  
  7 purchase totals = $989.38       $1,068.9559   $1,068.95   $1,068.95   $1,069.00