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	$82.38	12.211%	$92.4394	$92.44	$92.45	$92.40
Purchase #2	$57.34	5.789%	$60.6594	$60.66	$60.65	$60.70
Purchase #3	$99.91	11.390%	$111.2897	$111.29	$111.30	$111.30
Purchase #4	$250.91	6.605%	$267.4826	$267.48	$267.50	$267.50
Purchase #5	$178.90	6.613%	$190.7307	$190.73	$190.75	$190.70
Purchase #6	$105.29	11.321%	$117.2099	$117.21	$117.20	$117.20
Purchase #7	$238.64	8.199%	$258.2061	$258.21	$258.20	$258.20
7 purchase totals =	$1,013.37		$1,098.0178	$1,098.02	$1,098.05	$1,098.00