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	$245.35	10.663%	$271.5117	$271.51	$271.50	$271.50
Purchase #2	$30.35	7.341%	$32.578	$32.58	$32.60	$32.60
Purchase #3	$243.88	6.636%	$260.0639	$260.06	$260.05	$260.10
Purchase #4	$40.70	11.824%	$45.5124	$45.51	$45.50	$45.50
Purchase #5	$12.96	9.347%	$14.1714	$14.17	$14.15	$14.20
Purchase #6	$143.51	11.369%	$159.8257	$159.83	$159.85	$159.80
Purchase #7	$96.76	4.711%	$101.3184	$101.32	$101.30	$101.30
7 purchase totals =	$813.51		$884.9815	$884.98	$884.95	$885.00