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	$200.80	5.362%	$211.5669	$211.57	$211.55	$211.60
Purchase #2	$91.49	13.507%	$103.8476	$103.85	$103.85	$103.80
Purchase #3	$36.89	9.457%	$40.3787	$40.38	$40.40	$40.40
Purchase #4	$227.70	8.575%	$247.2253	$247.23	$247.25	$247.20
Purchase #5	$51.42	4.281%	$53.6213	$53.62	$53.60	$53.60
Purchase #6	$152.48	8.217%	$165.0093	$165.01	$165.00	$165.00
Purchase #7	$36.91	10.252%	$40.694	$40.69	$40.70	$40.70
7 purchase totals =	$797.69		$862.3431	$862.35	$862.35	$862.30