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	$19.75	5.472%	$20.8307	$20.83	$20.85	$20.80
Purchase #2	$149.75	5.595%	$158.1285	$158.13	$158.15	$158.10
Purchase #3	$222.34	7.157%	$238.2529	$238.25	$238.25	$238.30
Purchase #4	$144.28	6.271%	$153.3278	$153.33	$153.35	$153.30
Purchase #5	$247.90	6.186%	$263.2351	$263.24	$263.25	$263.20
Purchase #6	$141.84	3.193%	$146.369	$146.37	$146.35	$146.40
Purchase #7	$201.47	7.389%	$216.3566	$216.36	$216.35	$216.40
7 purchase totals =	$1,127.33		$1,196.5006	$1,196.51	$1,196.55	$1,196.50