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	$198.80	11.245%	$221.1551	$221.16	$221.15	$221.20
Purchase #2	$36.65	7.494%	$39.3966	$39.40	$39.40	$39.40
Purchase #3	$138.62	12.757%	$156.3038	$156.30	$156.30	$156.30
Purchase #4	$218.60	11.522%	$243.7871	$243.79	$243.80	$243.80
Purchase #5	$222.30	3.545%	$230.1805	$230.18	$230.20	$230.20
Purchase #6	$191.52	4.859%	$200.826	$200.83	$200.85	$200.80
Purchase #7	$89.78	11.198%	$99.8336	$99.83	$99.85	$99.80
7 purchase totals =	$1,096.27		$1,191.4827	$1,191.49	$1,191.55	$1,191.50