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	$242.30	7.588%	$260.6857	$260.69	$260.70	$260.70
Purchase #2	$134.58	12.335%	$151.1804	$151.18	$151.20	$151.20
Purchase #3	$148.90	12.490%	$167.4976	$167.50	$167.50	$167.50
Purchase #4	$143.27	6.507%	$152.5926	$152.59	$152.60	$152.60
Purchase #5	$117.27	13.461%	$133.0557	$133.06	$133.05	$133.10
Purchase #6	$165.71	3.539%	$171.5745	$171.57	$171.55	$171.60
Purchase #7	$86.98	4.233%	$90.6619	$90.66	$90.65	$90.70
7 purchase totals =	$1,039.01		$1,127.2484	$1,127.25	$1,127.25	$1,127.40