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	$185.60	5.809%	$196.3815	$196.38	$196.40	$196.40
Purchase #2	$199.79	3.766%	$207.3141	$207.31	$207.30	$207.30
Purchase #3	$242.55	13.376%	$274.9935	$274.99	$275.00	$275.00
Purchase #4	$40.32	4.471%	$42.1227	$42.12	$42.10	$42.10
Purchase #5	$111.95	13.478%	$127.0386	$127.04	$127.05	$127.00
Purchase #6	$143.98	3.863%	$149.5419	$149.54	$149.55	$149.50
Purchase #7	$15.37	6.449%	$16.3612	$16.36	$16.35	$16.40
7 purchase totals =	$939.56		$1,013.7535	$1,013.74	$1,013.75	$1,013.70