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	$9.29	12.516%	$10.4527	$10.45	$10.45	$10.50
Purchase #2	$79.28	3.733%	$82.2395	$82.24	$82.25	$82.20
Purchase #3	$209.74	4.446%	$219.065	$219.07	$219.05	$219.10
Purchase #4	$233.57	10.264%	$257.5436	$257.54	$257.55	$257.50
Purchase #5	$146.87	4.842%	$153.9814	$153.98	$154.00	$154.00
Purchase #6	$155.50	7.130%	$166.5872	$166.59	$166.60	$166.60
Purchase #7	$165.35	3.639%	$171.3671	$171.37	$171.35	$171.40
7 purchase totals =	$999.60		$1,061.2365	$1,061.24	$1,061.25	$1,061.30