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	$149.62	9.369%	$163.6379	$163.64	$163.65	$163.60
Purchase #2	$92.54	7.251%	$99.2501	$99.25	$99.25	$99.30
Purchase #3	$247.85	5.201%	$260.7407	$260.74	$260.75	$260.70
Purchase #4	$131.64	11.748%	$147.1051	$147.11	$147.10	$147.10
Purchase #5	$73.37	6.683%	$78.2733	$78.27	$78.25	$78.30
Purchase #6	$18.78	6.237%	$19.9513	$19.95	$19.95	$20.00
Purchase #7	$57.33	7.215%	$61.4664	$61.47	$61.45	$61.50
7 purchase totals =	$771.13		$830.4248	$830.43	$830.40	$830.50