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	$223.87	3.152%	$230.9264	$230.93	$230.95	$230.90
Purchase #2	$36.58	3.711%	$37.9375	$37.94	$37.95	$37.90
Purchase #3	$42.77	5.240%	$45.0111	$45.01	$45.00	$45.00
Purchase #4	$83.51	10.752%	$92.489	$92.49	$92.50	$92.50
Purchase #5	$8.47	11.643%	$9.4562	$9.46	$9.45	$9.50
Purchase #6	$241.39	12.793%	$272.271	$272.27	$272.25	$272.30
Purchase #7	$11.85	6.795%	$12.6552	$12.66	$12.65	$12.70
7 purchase totals =	$648.44		$700.7464	$700.76	$700.75	$700.80