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	$97.90	8.642%	$106.3605	$106.36	$106.35	$106.40
Purchase #2	$40.32	5.295%	$42.4549	$42.45	$42.45	$42.50
Purchase #3	$190.68	7.257%	$204.5176	$204.52	$204.50	$204.50
Purchase #4	$59.82	4.166%	$62.3121	$62.31	$62.30	$62.30
Purchase #5	$172.42	13.257%	$195.2777	$195.28	$195.30	$195.30
Purchase #6	$213.68	11.523%	$238.3023	$238.30	$238.30	$238.30
Purchase #7	$137.76	10.287%	$151.9314	$151.93	$151.95	$151.90
7 purchase totals =	$912.58		$1,001.1565	$1,001.15	$1,001.15	$1,001.20