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	$187.95	11.394%	$209.365	$209.37	$209.35	$209.40
Purchase #2	$103.81	4.471%	$108.4513	$108.45	$108.45	$108.50
Purchase #3	$146.75	13.425%	$166.4512	$166.45	$166.45	$166.50
Purchase #4	$113.84	12.249%	$127.7843	$127.78	$127.80	$127.80
Purchase #5	$39.92	7.699%	$42.9934	$42.99	$43.00	$43.00
Purchase #6	$112.63	12.648%	$126.8754	$126.88	$126.90	$126.90
Purchase #7	$164.46	12.743%	$185.4171	$185.42	$185.40	$185.40
7 purchase totals =	$869.36		$967.3377	$967.34	$967.35	$967.50