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 $63.35   9.373%   $69.2878   $69.29   $69.30   $69.30  
  Purchase #2 $227.94   11.197%   $253.4624   $253.46   $253.45   $253.50  
  Purchase #3 $115.72   8.102%   $125.0956   $125.10   $125.10   $125.10  
  Purchase #4 $15.73   7.329%   $16.8829   $16.88   $16.90   $16.90  
  Purchase #5 $225.36   8.396%   $244.2812   $244.28   $244.30   $244.30  
  Purchase #6 $86.57   6.837%   $92.4888   $92.49   $92.50   $92.50  
  Purchase #7 $199.65   6.604%   $212.8349   $212.83   $212.85   $212.80  
  7 purchase totals = $934.32       $1,014.3336   $1,014.33   $1,014.40   $1,014.40