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	$153.75	10.428%	$169.7831	$169.78	$169.80	$169.80
Purchase #2	$207.25	11.205%	$230.4724	$230.47	$230.45	$230.50
Purchase #3	$51.53	5.866%	$54.5527	$54.55	$54.55	$54.60
Purchase #4	$112.38	4.368%	$117.2888	$117.29	$117.30	$117.30
Purchase #5	$61.35	10.697%	$67.9126	$67.91	$67.90	$67.90
Purchase #6	$250.74	7.162%	$268.698	$268.70	$268.70	$268.70
Purchase #7	$89.43	10.749%	$99.0428	$99.04	$99.05	$99.00
7 purchase totals =	$926.43		$1,007.7504	$1,007.74	$1,007.75	$1,007.80