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	$105.76	8.688%	$114.9484	$114.95	$114.95	$114.90
Purchase #2	$32.61	9.670%	$35.7634	$35.76	$35.75	$35.80
Purchase #3	$32.49	4.556%	$33.9702	$33.97	$33.95	$34.00
Purchase #4	$118.52	4.468%	$123.8155	$123.82	$123.80	$123.80
Purchase #5	$122.76	9.851%	$134.8531	$134.85	$134.85	$134.90
Purchase #6	$227.25	7.218%	$243.6529	$243.65	$243.65	$243.70
Purchase #7	$52.83	3.435%	$54.6447	$54.64	$54.65	$54.60
7 purchase totals =	$692.22		$741.6482	$741.64	$741.60	$741.70