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	$140.79	11.501%	$156.9823	$156.98	$157.00	$157.00
Purchase #2	$34.94	10.362%	$38.5605	$38.56	$38.55	$38.60
Purchase #3	$151.84	5.696%	$160.4888	$160.49	$160.50	$160.50
Purchase #4	$173.74	13.229%	$196.7241	$196.72	$196.70	$196.70
Purchase #5	$186.93	13.225%	$211.6515	$211.65	$211.65	$211.70
Purchase #6	$61.64	13.827%	$70.163	$70.16	$70.15	$70.20
Purchase #7	$227.84	10.348%	$251.4169	$251.42	$251.40	$251.40
7 purchase totals =	$977.72		$1,085.9871	$1,085.98	$1,085.95	$1,086.10