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	$186.93	13.479%	$212.1263	$212.13	$212.15	$212.10
Purchase #2	$173.69	6.824%	$185.5426	$185.54	$185.55	$185.50
Purchase #3	$152.80	12.778%	$172.3248	$172.32	$172.30	$172.30
Purchase #4	$171.89	9.501%	$188.2213	$188.22	$188.20	$188.20
Purchase #5	$231.74	9.469%	$253.6835	$253.68	$253.70	$253.70
Purchase #6	$56.34	9.191%	$61.5182	$61.52	$61.50	$61.50
Purchase #7	$38.37	5.247%	$40.3833	$40.38	$40.40	$40.40
7 purchase totals =	$1,011.76		$1,113.8000	$1,113.79	$1,113.80	$1,113.70