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	$48.32	4.312%	$50.4036	$50.40	$50.40	$50.40
Purchase #2	$68.31	4.744%	$71.5506	$71.55	$71.55	$71.60
Purchase #3	$23.75	7.308%	$25.4857	$25.49	$25.50	$25.50
Purchase #4	$78.93	13.735%	$89.771	$89.77	$89.75	$89.80
Purchase #5	$212.70	3.445%	$220.0275	$220.03	$220.05	$220.00
Purchase #6	$146.82	9.560%	$160.856	$160.86	$160.85	$160.90
Purchase #7	$223.35	9.568%	$244.7201	$244.72	$244.70	$244.70
7 purchase totals =	$802.18		$862.8145	$862.82	$862.80	$862.90