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 $59.52   4.800%   $62.377   $62.38   $62.40   $62.40  
  Purchase #2 $41.34   9.654%   $45.331   $45.33   $45.35   $45.30  
  Purchase #3 $200.72   11.561%   $223.9252   $223.93   $223.95   $223.90  
  Purchase #4 $21.38   11.287%   $23.7932   $23.79   $23.80   $23.80  
  Purchase #5 $216.99   4.648%   $227.0757   $227.08   $227.10   $227.10  
  Purchase #6 $212.43   10.518%   $234.7734   $234.77   $234.75   $234.80  
  Purchase #7 $44.72   12.438%   $50.2823   $50.28   $50.30   $50.30  
  7 purchase totals = $797.10       $867.5578   $867.56   $867.65   $867.60