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	$155.94	4.319%	$162.675	$162.68	$162.70	$162.70
Purchase #2	$24.66	6.469%	$26.2553	$26.26	$26.25	$26.30
Purchase #3	$108.57	3.130%	$111.9682	$111.97	$111.95	$112.00
Purchase #4	$111.27	5.404%	$117.283	$117.28	$117.30	$117.30
Purchase #5	$71.69	12.392%	$80.5738	$80.57	$80.55	$80.60
Purchase #6	$196.64	7.111%	$210.6231	$210.62	$210.60	$210.60
Purchase #7	$84.95	6.168%	$90.1897	$90.19	$90.20	$90.20
7 purchase totals =	$753.72		$799.5681	$799.57	$799.55	$799.70