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	$141.79	3.396%	$146.6052	$146.61	$146.60	$146.60
Purchase #2	$91.72	5.214%	$96.5023	$96.50	$96.50	$96.50
Purchase #3	$101.69	11.408%	$113.2908	$113.29	$113.30	$113.30
Purchase #4	$163.83	5.430%	$172.726	$172.73	$172.75	$172.70
Purchase #5	$96.34	4.370%	$100.5501	$100.55	$100.55	$100.60
Purchase #6	$38.80	3.399%	$40.1188	$40.12	$40.10	$40.10
Purchase #7	$159.87	3.800%	$165.9451	$165.95	$165.95	$165.90
7 purchase totals =	$794.04		$835.7383	$835.75	$835.75	$835.70