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	$73.27	7.405%	$78.6956	$78.70	$78.70	$78.70
Purchase #2	$69.35	3.444%	$71.7384	$71.74	$71.75	$71.70
Purchase #3	$38.40	13.390%	$43.5418	$43.54	$43.55	$43.50
Purchase #4	$49.30	13.479%	$55.9451	$55.95	$55.95	$55.90
Purchase #5	$76.78	11.353%	$85.4968	$85.50	$85.50	$85.50
Purchase #6	$167.97	3.344%	$173.5869	$173.59	$173.60	$173.60
Purchase #7	$134.45	10.394%	$148.4247	$148.42	$148.40	$148.40
7 purchase totals =	$609.52		$657.4293	$657.44	$657.45	$657.30