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	$181.83	8.118%	$196.591	$196.59	$196.60	$196.60
Purchase #2	$217.31	3.413%	$224.7268	$224.73	$224.75	$224.70
Purchase #3	$37.30	4.632%	$39.0277	$39.03	$39.05	$39.00
Purchase #4	$120.72	4.793%	$126.5061	$126.51	$126.50	$126.50
Purchase #5	$146.72	3.217%	$151.44	$151.44	$151.45	$151.40
Purchase #6	$79.41	4.689%	$83.1335	$83.13	$83.15	$83.10
Purchase #7	$35.89	3.660%	$37.2036	$37.20	$37.20	$37.20
7 purchase totals =	$819.18		$858.6287	$858.63	$858.70	$858.50