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 $61.25   12.575%   $68.9522   $68.95   $68.95   $69.00  
  Purchase #2 $238.70   5.187%   $251.0814   $251.08   $251.10   $251.10  
  Purchase #3 $183.87   11.239%   $204.5351   $204.54   $204.55   $204.50  
  Purchase #4 $42.84   4.436%   $44.7404   $44.74   $44.75   $44.70  
  Purchase #5 $204.32   6.529%   $217.6601   $217.66   $217.65   $217.70  
  Purchase #6 $90.44   12.174%   $101.4502   $101.45   $101.45   $101.50  
  Purchase #7 $216.95   12.567%   $244.2141   $244.21   $244.20   $244.20  
  7 purchase totals = $1,038.37       $1,132.6335   $1,132.63   $1,132.65   $1,132.70