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	$64.41	11.510%	$71.8236	$71.82	$71.80	$71.80
Purchase #2	$247.91	13.234%	$280.7184	$280.72	$280.70	$280.70
Purchase #3	$158.82	5.181%	$167.0485	$167.05	$167.05	$167.00
Purchase #4	$49.28	11.477%	$54.9359	$54.94	$54.95	$54.90
Purchase #5	$14.69	5.166%	$15.4489	$15.45	$15.45	$15.40
Purchase #6	$93.32	3.414%	$96.5059	$96.51	$96.50	$96.50
Purchase #7	$198.72	8.578%	$215.7662	$215.77	$215.75	$215.80
7 purchase totals =	$827.15		$902.2474	$902.26	$902.20	$902.10