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	$33.32	13.116%	$37.6903	$37.69	$37.70	$37.70
Purchase #2	$54.75	12.605%	$61.6512	$61.65	$61.65	$61.70
Purchase #3	$188.51	4.312%	$196.6386	$196.64	$196.65	$196.60
Purchase #4	$67.66	9.510%	$74.0945	$74.09	$74.10	$74.10
Purchase #5	$183.96	3.869%	$191.0774	$191.08	$191.10	$191.10
Purchase #6	$160.93	9.644%	$176.4501	$176.45	$176.45	$176.50
Purchase #7	$25.64	12.117%	$28.7468	$28.75	$28.75	$28.70
7 purchase totals =	$714.77		$766.3489	$766.35	$766.40	$766.40