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	$99.89	5.384%	$105.2681	$105.27	$105.25	$105.30
Purchase #2	$188.46	11.384%	$209.9143	$209.91	$209.90	$209.90
Purchase #3	$51.80	13.439%	$58.7614	$58.76	$58.75	$58.80
Purchase #4	$100.47	11.346%	$111.8693	$111.87	$111.85	$111.90
Purchase #5	$243.67	3.526%	$252.2618	$252.26	$252.25	$252.30
Purchase #6	$197.43	5.836%	$208.952	$208.95	$208.95	$209.00
Purchase #7	$189.94	8.221%	$205.555	$205.56	$205.55	$205.60
7 purchase totals =	$1,071.66		$1,152.5819	$1,152.58	$1,152.50	$1,152.80