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	$130.53	12.173%	$146.4194	$146.42	$146.40	$146.40
Purchase #2	$230.72	4.574%	$241.2731	$241.27	$241.25	$241.30
Purchase #3	$24.67	3.557%	$25.5475	$25.55	$25.55	$25.50
Purchase #4	$150.33	5.662%	$158.8417	$158.84	$158.85	$158.80
Purchase #5	$136.89	6.396%	$145.6455	$145.65	$145.65	$145.60
Purchase #6	$135.41	12.514%	$152.3552	$152.36	$152.35	$152.40
Purchase #7	$205.37	13.760%	$233.6289	$233.63	$233.65	$233.60
7 purchase totals =	$1,013.92		$1,103.7113	$1,103.72	$1,103.70	$1,103.60