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	$144.74	7.636%	$155.7923	$155.79	$155.80	$155.80
Purchase #2	$55.92	9.593%	$61.2844	$61.28	$61.30	$61.30
Purchase #3	$147.96	5.470%	$156.0534	$156.05	$156.05	$156.10
Purchase #4	$222.86	3.404%	$230.4462	$230.45	$230.45	$230.40
Purchase #5	$159.91	7.805%	$172.391	$172.39	$172.40	$172.40
Purchase #6	$49.77	7.770%	$53.6371	$53.64	$53.65	$53.60
Purchase #7	$65.48	4.424%	$68.3768	$68.38	$68.40	$68.40
7 purchase totals =	$846.64		$897.9812	$897.98	$898.05	$898.00