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 $202.31   5.782%   $214.0076   $214.01   $214.00   $214.00  
  Purchase #2 $86.50   11.334%   $96.3039   $96.30   $96.30   $96.30  
  Purchase #3 $183.63   7.595%   $197.5767   $197.58   $197.60   $197.60  
  Purchase #4 $95.96   6.149%   $101.8606   $101.86   $101.85   $101.90  
  Purchase #5 $202.76   11.273%   $225.6171   $225.62   $225.60   $225.60  
  Purchase #6 $227.88   7.673%   $245.3652   $245.37   $245.35   $245.40  
  Purchase #7 $52.87   4.604%   $55.3041   $55.30   $55.30   $55.30  
  7 purchase totals = $1,051.91       $1,136.0352   $1,136.04   $1,136.00   $1,136.10