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	$98.66	5.708%	$104.2915	$104.29	$104.30	$104.30
Purchase #2	$143.26	6.237%	$152.1951	$152.20	$152.20	$152.20
Purchase #3	$51.93	7.298%	$55.7199	$55.72	$55.70	$55.70
Purchase #4	$163.52	12.338%	$183.6951	$183.70	$183.70	$183.70
Purchase #5	$150.28	10.339%	$165.8174	$165.82	$165.80	$165.80
Purchase #6	$12.70	4.650%	$13.2906	$13.29	$13.30	$13.30
Purchase #7	$106.56	4.816%	$111.6919	$111.69	$111.70	$111.70
7 purchase totals =	$726.91		$786.7015	$786.71	$786.70	$786.70