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	$229.71	6.791%	$245.3096	$245.31	$245.30	$245.30
Purchase #2	$212.67	10.243%	$234.4538	$234.45	$234.45	$234.50
Purchase #3	$172.94	3.310%	$178.6643	$178.66	$178.65	$178.70
Purchase #4	$190.48	11.472%	$212.3319	$212.33	$212.35	$212.30
Purchase #5	$104.93	6.182%	$111.4168	$111.42	$111.40	$111.40
Purchase #6	$47.92	10.517%	$52.9597	$52.96	$52.95	$53.00
Purchase #7	$165.30	10.314%	$182.349	$182.35	$182.35	$182.30
7 purchase totals =	$1,123.95		$1,217.4851	$1,217.48	$1,217.45	$1,217.50