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	$147.83	5.846%	$156.4721	$156.47	$156.45	$156.50
Purchase #2	$45.43	6.778%	$48.5092	$48.51	$48.50	$48.50
Purchase #3	$119.71	3.295%	$123.6544	$123.65	$123.65	$123.70
Purchase #4	$104.83	3.327%	$108.3177	$108.32	$108.30	$108.30
Purchase #5	$155.37	7.822%	$167.523	$167.52	$167.50	$167.50
Purchase #6	$130.31	6.600%	$138.9105	$138.91	$138.90	$138.90
Purchase #7	$223.99	5.739%	$236.8448	$236.84	$236.85	$236.80
7 purchase totals =	$927.47		$980.2317	$980.22	$980.15	$980.20