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	$225.57	8.581%	$244.9262	$244.93	$244.95	$244.90
Purchase #2	$126.90	8.260%	$137.3819	$137.38	$137.40	$137.40
Purchase #3	$53.85	12.462%	$60.5608	$60.56	$60.55	$60.60
Purchase #4	$223.46	5.599%	$235.9715	$235.97	$235.95	$236.00
Purchase #5	$55.74	7.535%	$59.94	$59.94	$59.95	$59.90
Purchase #6	$185.46	13.463%	$210.4285	$210.43	$210.45	$210.40
Purchase #7	$49.48	6.521%	$52.7066	$52.71	$52.70	$52.70
7 purchase totals =	$920.46		$1,001.9155	$1,001.92	$1,001.95	$1,001.90