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	$134.77	12.135%	$151.1243	$151.12	$151.10	$151.10
Purchase #2	$243.96	9.715%	$267.6607	$267.66	$267.65	$267.70
Purchase #3	$240.64	4.732%	$252.0271	$252.03	$252.05	$252.00
Purchase #4	$240.97	5.218%	$253.5438	$253.54	$253.55	$253.50
Purchase #5	$72.88	4.808%	$76.3841	$76.38	$76.40	$76.40
Purchase #6	$55.71	9.183%	$60.8258	$60.83	$60.85	$60.80
Purchase #7	$97.86	13.594%	$111.1631	$111.16	$111.15	$111.20
7 purchase totals =	$1,086.79		$1,172.7289	$1,172.72	$1,172.75	$1,172.70