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	$58.59	10.476%	$64.7279	$64.73	$64.75	$64.70
Purchase #2	$27.54	6.272%	$29.2673	$29.27	$29.25	$29.30
Purchase #3	$211.93	8.326%	$229.5753	$229.58	$229.60	$229.60
Purchase #4	$117.85	8.741%	$128.1513	$128.15	$128.15	$128.20
Purchase #5	$115.32	13.502%	$130.8905	$130.89	$130.90	$130.90
Purchase #6	$49.42	11.128%	$54.9195	$54.92	$54.90	$54.90
Purchase #7	$51.41	6.169%	$54.5815	$54.58	$54.60	$54.60
7 purchase totals =	$632.06		$692.1133	$692.12	$692.15	$692.20