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	$196.82	7.383%	$211.3512	$211.35	$211.35	$211.40
Purchase #2	$65.28	13.855%	$74.3245	$74.32	$74.30	$74.30
Purchase #3	$214.83	12.827%	$242.3862	$242.39	$242.40	$242.40
Purchase #4	$28.86	13.652%	$32.8	$32.80	$32.80	$32.80
Purchase #5	$78.47	6.710%	$83.7353	$83.74	$83.75	$83.70
Purchase #6	$249.86	3.423%	$258.4127	$258.41	$258.40	$258.40
Purchase #7	$111.39	12.680%	$125.5143	$125.51	$125.50	$125.50
7 purchase totals =	$945.51		$1,028.5242	$1,028.52	$1,028.50	$1,028.50