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	$184.91	3.162%	$190.7569	$190.76	$190.75	$190.80
Purchase #2	$112.40	4.376%	$117.3186	$117.32	$117.30	$117.30
Purchase #3	$182.45	6.418%	$194.1596	$194.16	$194.15	$194.20
Purchase #4	$130.67	10.513%	$144.4073	$144.41	$144.40	$144.40
Purchase #5	$148.69	6.527%	$158.395	$158.40	$158.40	$158.40
Purchase #6	$235.27	8.280%	$254.7504	$254.75	$254.75	$254.80
Purchase #7	$40.38	11.490%	$45.0197	$45.02	$45.00	$45.00
7 purchase totals =	$1,034.77		$1,104.8075	$1,104.82	$1,104.75	$1,104.90