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	$243.43	8.456%	$264.0144	$264.01	$264.00	$264.00
Purchase #2	$101.73	8.681%	$110.5612	$110.56	$110.55	$110.60
Purchase #3	$122.76	3.748%	$127.361	$127.36	$127.35	$127.40
Purchase #4	$134.89	5.388%	$142.1579	$142.16	$142.15	$142.20
Purchase #5	$32.97	3.386%	$34.0864	$34.09	$34.10	$34.10
Purchase #6	$120.72	13.748%	$137.3166	$137.32	$137.30	$137.30
Purchase #7	$89.26	12.394%	$100.3229	$100.32	$100.30	$100.30
7 purchase totals =	$845.76		$915.8204	$915.82	$915.75	$915.90