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	$187.98	5.211%	$197.7756	$197.78	$197.80	$197.80
Purchase #2	$72.32	5.290%	$76.1457	$76.15	$76.15	$76.10
Purchase #3	$35.45	10.282%	$39.095	$39.10	$39.10	$39.10
Purchase #4	$30.74	11.616%	$34.3108	$34.31	$34.30	$34.30
Purchase #5	$152.80	3.422%	$158.0288	$158.03	$158.05	$158.00
Purchase #6	$97.87	13.724%	$111.3017	$111.30	$111.30	$111.30
Purchase #7	$168.53	6.721%	$179.8569	$179.86	$179.85	$179.90
7 purchase totals =	$745.69		$796.5145	$796.53	$796.55	$796.50