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 $196.64   13.680%   $223.5404   $223.54   $223.55   $223.50  
  Purchase #2 $198.51   8.804%   $215.9868   $215.99   $216.00   $216.00  
  Purchase #3 $175.72   4.629%   $183.8541   $183.85   $183.85   $183.90  
  Purchase #4 $110.29   11.458%   $122.927   $122.93   $122.95   $122.90  
  Purchase #5 $241.32   6.229%   $256.3518   $256.35   $256.35   $256.40  
  Purchase #6 $210.37   9.180%   $229.682   $229.68   $229.70   $229.70  
  Purchase #7 $226.63   7.668%   $244.008   $244.01   $244.00   $244.00  
  7 purchase totals = $1,359.48       $1,476.3501   $1,476.35   $1,476.40   $1,476.40