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	$153.91	5.333%	$162.118	$162.12	$162.10	$162.10
Purchase #2	$215.34	12.535%	$242.3329	$242.33	$242.35	$242.30
Purchase #3	$88.84	8.172%	$96.1	$96.10	$96.10	$96.10
Purchase #4	$155.89	4.178%	$162.4031	$162.40	$162.40	$162.40
Purchase #5	$104.63	8.830%	$113.8688	$113.87	$113.85	$113.90
Purchase #6	$126.70	13.194%	$143.4168	$143.42	$143.40	$143.40
Purchase #7	$136.74	6.787%	$146.0205	$146.02	$146.00	$146.00
7 purchase totals =	$982.05		$1,066.2601	$1,066.26	$1,066.20	$1,066.20