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	$132.35	10.537%	$146.2957	$146.30	$146.30	$146.30
Purchase #2	$174.34	4.150%	$181.5751	$181.58	$181.60	$181.60
Purchase #3	$200.64	5.203%	$211.0793	$211.08	$211.10	$211.10
Purchase #4	$54.78	8.399%	$59.381	$59.38	$59.40	$59.40
Purchase #5	$226.31	6.501%	$241.0224	$241.02	$241.00	$241.00
Purchase #6	$189.36	11.464%	$211.0682	$211.07	$211.05	$211.10
Purchase #7	$123.82	13.835%	$140.9505	$140.95	$140.95	$141.00
7 purchase totals =	$1,101.60		$1,191.3722	$1,191.38	$1,191.40	$1,191.50