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 $219.41   11.528%   $244.7036   $244.70   $244.70   $244.70  
  Purchase #2 $166.63   5.754%   $176.2179   $176.22   $176.20   $176.20  
  Purchase #3 $51.58   7.527%   $55.4624   $55.46   $55.45   $55.50  
  Purchase #4 $46.89   6.130%   $49.7644   $49.76   $49.75   $49.80  
  Purchase #5 $229.49   11.658%   $256.2439   $256.24   $256.25   $256.20  
  Purchase #6 $184.88   11.698%   $206.5073   $206.51   $206.50   $206.50  
  Purchase #7 $34.53   7.282%   $37.0445   $37.04   $37.05   $37.00  
  7 purchase totals = $933.41       $1,025.9440   $1,025.93   $1,025.90   $1,025.90