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	$129.34	13.372%	$146.6353	$146.64	$146.65	$146.60
Purchase #2	$139.71	9.451%	$152.914	$152.91	$152.90	$152.90
Purchase #3	$154.96	3.615%	$160.5618	$160.56	$160.55	$160.60
Purchase #4	$225.53	3.397%	$233.1913	$233.19	$233.20	$233.20
Purchase #5	$33.66	10.683%	$37.2559	$37.26	$37.25	$37.30
Purchase #6	$226.49	11.105%	$251.6417	$251.64	$251.65	$251.60
Purchase #7	$221.55	8.251%	$239.8301	$239.83	$239.85	$239.80
7 purchase totals =	$1,131.24		$1,222.0301	$1,222.03	$1,222.05	$1,222.00