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 $86.31   11.169%   $95.95   $95.95   $95.95   $96.00  
  Purchase #2 $126.50   10.389%   $139.6421   $139.64   $139.65   $139.60  
  Purchase #3 $141.79   9.526%   $155.2969   $155.30   $155.30   $155.30  
  Purchase #4 $150.39   6.184%   $159.6901   $159.69   $159.70   $159.70  
  Purchase #5 $110.40   12.444%   $124.1382   $124.14   $124.15   $124.10  
  Purchase #6 $49.47   9.231%   $54.0366   $54.04   $54.05   $54.00  
  Purchase #7 $22.27   3.291%   $23.0029   $23.00   $23.00   $23.00  
  7 purchase totals = $687.13       $751.7568   $751.76   $751.80   $751.70