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	$207.78	11.721%	$232.1339	$232.13	$232.15	$232.10
Purchase #2	$29.28	13.577%	$33.2553	$33.26	$33.25	$33.30
Purchase #3	$196.32	10.766%	$217.4558	$217.46	$217.45	$217.50
Purchase #4	$170.56	11.676%	$190.4746	$190.47	$190.45	$190.50
Purchase #5	$199.42	8.255%	$215.8821	$215.88	$215.90	$215.90
Purchase #6	$141.62	4.783%	$148.3937	$148.39	$148.40	$148.40
Purchase #7	$89.42	6.764%	$95.4684	$95.47	$95.45	$95.50
7 purchase totals =	$1,034.40		$1,133.0638	$1,133.06	$1,133.05	$1,133.20