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	$156.85	13.584%	$178.1565	$178.16	$178.15	$178.20
Purchase #2	$171.42	13.599%	$194.7314	$194.73	$194.75	$194.70
Purchase #3	$246.89	9.542%	$270.4482	$270.45	$270.45	$270.40
Purchase #4	$48.89	11.729%	$54.6243	$54.62	$54.60	$54.60
Purchase #5	$185.38	8.178%	$200.5404	$200.54	$200.55	$200.50
Purchase #6	$195.84	13.502%	$222.2823	$222.28	$222.30	$222.30
Purchase #7	$219.95	3.536%	$227.7274	$227.73	$227.75	$227.70
7 purchase totals =	$1,225.22		$1,348.5105	$1,348.51	$1,348.55	$1,348.40