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	$247.39	6.555%	$263.6064	$263.61	$263.60	$263.60
Purchase #2	$146.78	4.613%	$153.551	$153.55	$153.55	$153.60
Purchase #3	$246.34	11.106%	$273.6985	$273.70	$273.70	$273.70
Purchase #4	$90.41	10.454%	$99.8615	$99.86	$99.85	$99.90
Purchase #5	$72.99	8.155%	$78.9423	$78.94	$78.95	$78.90
Purchase #6	$205.33	10.650%	$227.1976	$227.20	$227.20	$227.20
Purchase #7	$139.42	3.612%	$144.4559	$144.46	$144.45	$144.50
7 purchase totals =	$1,148.66		$1,241.3132	$1,241.32	$1,241.30	$1,241.40