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	$130.59	11.857%	$146.0741	$146.07	$146.05	$146.10
Purchase #2	$42.45	12.248%	$47.6493	$47.65	$47.65	$47.60
Purchase #3	$84.25	9.857%	$92.5545	$92.55	$92.55	$92.60
Purchase #4	$161.86	4.365%	$168.9252	$168.93	$168.95	$168.90
Purchase #5	$76.25	11.615%	$85.1064	$85.11	$85.10	$85.10
Purchase #6	$242.89	3.452%	$251.2746	$251.27	$251.25	$251.30
Purchase #7	$250.85	13.279%	$284.1604	$284.16	$284.15	$284.20
7 purchase totals =	$989.14		$1,075.7445	$1,075.74	$1,075.70	$1,075.80