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	$147.93	6.575%	$157.6564	$157.66	$157.65	$157.70
Purchase #2	$153.98	12.613%	$173.4015	$173.40	$173.40	$173.40
Purchase #3	$89.40	12.199%	$100.3059	$100.31	$100.30	$100.30
Purchase #4	$239.39	11.263%	$266.3525	$266.35	$266.35	$266.40
Purchase #5	$70.31	3.595%	$72.8376	$72.84	$72.85	$72.80
Purchase #6	$66.42	5.780%	$70.2591	$70.26	$70.25	$70.30
Purchase #7	$97.69	3.738%	$101.3417	$101.34	$101.35	$101.30
7 purchase totals =	$865.12		$942.1547	$942.16	$942.15	$942.20