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	$232.84	8.681%	$253.0528	$253.05	$253.05	$253.10
Purchase #2	$90.55	12.344%	$101.7275	$101.73	$101.75	$101.70
Purchase #3	$139.63	10.201%	$153.8737	$153.87	$153.85	$153.90
Purchase #4	$235.55	13.405%	$267.1255	$267.13	$267.15	$267.10
Purchase #5	$49.63	11.806%	$55.4893	$55.49	$55.50	$55.50
Purchase #6	$53.50	11.729%	$59.775	$59.78	$59.80	$59.80
Purchase #7	$176.94	8.228%	$191.4986	$191.50	$191.50	$191.50
7 purchase totals =	$978.64		$1,082.5424	$1,082.55	$1,082.60	$1,082.60