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	$142.71	6.413%	$151.862	$151.86	$151.85	$151.90
Purchase #2	$160.43	8.199%	$173.5837	$173.58	$173.60	$173.60
Purchase #3	$29.74	4.669%	$31.1286	$31.13	$31.15	$31.10
Purchase #4	$105.70	3.463%	$109.3604	$109.36	$109.35	$109.40
Purchase #5	$83.29	7.245%	$89.3244	$89.32	$89.30	$89.30
Purchase #6	$55.72	6.527%	$59.3568	$59.36	$59.35	$59.40
Purchase #7	$15.93	6.250%	$16.9256	$16.93	$16.95	$16.90
7 purchase totals =	$593.52		$631.5415	$631.54	$631.55	$631.60