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	$130.47	10.131%	$143.6879	$143.69	$143.70	$143.70
Purchase #2	$217.63	12.275%	$244.3441	$244.34	$244.35	$244.30
Purchase #3	$238.60	6.815%	$254.8606	$254.86	$254.85	$254.90
Purchase #4	$138.81	13.843%	$158.0255	$158.03	$158.05	$158.00
Purchase #5	$168.27	11.741%	$188.0266	$188.03	$188.05	$188.00
Purchase #6	$90.55	6.642%	$96.5643	$96.56	$96.55	$96.60
Purchase #7	$77.92	11.789%	$87.106	$87.11	$87.10	$87.10
7 purchase totals =	$1,062.25		$1,172.6150	$1,172.62	$1,172.65	$1,172.60