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	$158.30	11.169%	$175.9805	$175.98	$176.00	$176.00
Purchase #2	$171.65	9.594%	$188.1181	$188.12	$188.10	$188.10
Purchase #3	$132.64	5.752%	$140.2695	$140.27	$140.25	$140.30
Purchase #4	$98.82	10.702%	$109.3957	$109.40	$109.40	$109.40
Purchase #5	$81.32	11.733%	$90.8613	$90.86	$90.85	$90.90
Purchase #6	$49.36	10.157%	$54.3735	$54.37	$54.35	$54.40
Purchase #7	$47.77	11.497%	$53.2621	$53.26	$53.25	$53.30
7 purchase totals =	$739.86		$812.2607	$812.26	$812.20	$812.40