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 $60.33   3.267%   $62.301   $62.30   $62.30   $62.30  
  Purchase #2 $55.45   6.112%   $58.8391   $58.84   $58.85   $58.80  
  Purchase #3 $110.36   4.658%   $115.5006   $115.50   $115.50   $115.50  
  Purchase #4 $222.25   10.181%   $244.8773   $244.88   $244.90   $244.90  
  Purchase #5 $212.61   6.310%   $226.0257   $226.03   $226.05   $226.00  
  Purchase #6 $106.70   8.192%   $115.4409   $115.44   $115.45   $115.40  
  Purchase #7 $184.67   3.516%   $191.163   $191.16   $191.15   $191.20  
  7 purchase totals = $952.37       $1,014.1476   $1,014.15   $1,014.20   $1,014.10