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	$55.89	9.348%	$61.1146	$61.11	$61.10	$61.10
Purchase #2	$37.79	6.670%	$40.3106	$40.31	$40.30	$40.30
Purchase #3	$54.44	5.498%	$57.4331	$57.43	$57.45	$57.40
Purchase #4	$60.71	10.243%	$66.9285	$66.93	$66.95	$66.90
Purchase #5	$149.69	4.395%	$156.2689	$156.27	$156.25	$156.30
Purchase #6	$153.64	4.632%	$160.7566	$160.76	$160.75	$160.80
Purchase #7	$142.53	4.820%	$149.3999	$149.40	$149.40	$149.40
7 purchase totals =	$654.69		$692.2122	$692.21	$692.20	$692.20