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	$66.70	9.451%	$73.0038	$73.00	$73.00	$73.00
Purchase #2	$40.94	13.680%	$46.5406	$46.54	$46.55	$46.50
Purchase #3	$162.49	6.187%	$172.5433	$172.54	$172.55	$172.50
Purchase #4	$156.66	3.615%	$162.3233	$162.32	$162.30	$162.30
Purchase #5	$96.54	8.793%	$105.0288	$105.03	$105.05	$105.00
Purchase #6	$193.74	8.543%	$210.2912	$210.29	$210.30	$210.30
Purchase #7	$11.43	6.332%	$12.1537	$12.15	$12.15	$12.20
7 purchase totals =	$728.50		$781.8847	$781.87	$781.90	$781.80