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	$238.72	7.726%	$257.1635	$257.16	$257.15	$257.20
Purchase #2	$145.26	4.842%	$152.2935	$152.29	$152.30	$152.30
Purchase #3	$126.81	11.492%	$141.383	$141.38	$141.40	$141.40
Purchase #4	$210.83	6.379%	$224.2788	$224.28	$224.30	$224.30
Purchase #5	$250.71	13.712%	$285.0874	$285.09	$285.10	$285.10
Purchase #6	$60.62	3.409%	$62.6865	$62.69	$62.70	$62.70
Purchase #7	$48.27	5.463%	$50.907	$50.91	$50.90	$50.90
7 purchase totals =	$1,081.22		$1,173.7997	$1,173.80	$1,173.85	$1,173.90