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	$52.62	11.534%	$58.6892	$58.69	$58.70	$58.70
Purchase #2	$111.65	10.428%	$123.2929	$123.29	$123.30	$123.30
Purchase #3	$167.78	13.517%	$190.4588	$190.46	$190.45	$190.50
Purchase #4	$6.56	7.568%	$7.0565	$7.06	$7.05	$7.10
Purchase #5	$246.71	10.525%	$272.6762	$272.68	$272.70	$272.70
Purchase #6	$54.95	10.637%	$60.795	$60.80	$60.80	$60.80
Purchase #7	$67.35	8.156%	$72.8431	$72.84	$72.85	$72.80
7 purchase totals =	$707.62		$785.8117	$785.82	$785.85	$785.90