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	$244.67	6.518%	$260.6176	$260.62	$260.60	$260.60
Purchase #2	$209.99	13.675%	$238.7061	$238.71	$238.70	$238.70
Purchase #3	$226.96	10.268%	$250.2643	$250.26	$250.25	$250.30
Purchase #4	$229.97	3.673%	$238.4168	$238.42	$238.40	$238.40
Purchase #5	$156.73	6.642%	$167.14	$167.14	$167.15	$167.10
Purchase #6	$55.75	7.510%	$59.9368	$59.94	$59.95	$59.90
Purchase #7	$149.39	13.501%	$169.5591	$169.56	$169.55	$169.60
7 purchase totals =	$1,273.46		$1,384.6407	$1,384.65	$1,384.60	$1,384.60