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	$79.54	7.520%	$85.5214	$85.52	$85.50	$85.50
Purchase #2	$185.59	8.796%	$201.9145	$201.91	$201.90	$201.90
Purchase #3	$117.83	8.200%	$127.4921	$127.49	$127.50	$127.50
Purchase #4	$117.91	13.160%	$133.427	$133.43	$133.45	$133.40
Purchase #5	$9.39	12.358%	$10.5504	$10.55	$10.55	$10.60
Purchase #6	$102.77	8.411%	$111.414	$111.41	$111.40	$111.40
Purchase #7	$57.31	13.466%	$65.0274	$65.03	$65.05	$65.00
7 purchase totals =	$670.34		$735.3468	$735.34	$735.35	$735.30