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 $59.39   4.263%   $61.9218   $61.92   $61.90   $61.90  
  Purchase #2 $223.88   10.417%   $247.2016   $247.20   $247.20   $247.20  
  Purchase #3 $178.88   11.725%   $199.8537   $199.85   $199.85   $199.90  
  Purchase #4 $82.47   5.591%   $87.0809   $87.08   $87.10   $87.10  
  Purchase #5 $125.51   10.777%   $139.0362   $139.04   $139.05   $139.00  
  Purchase #6 $232.67   7.713%   $250.6158   $250.62   $250.60   $250.60  
  Purchase #7 $20.29   8.222%   $21.9582   $21.96   $21.95   $22.00  
  7 purchase totals = $923.09       $1,007.6682   $1,007.67   $1,007.65   $1,007.70