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	$167.53	10.263%	$184.7236	$184.72	$184.70	$184.70
Purchase #2	$104.88	6.242%	$111.4266	$111.43	$111.45	$111.40
Purchase #3	$25.67	6.453%	$27.3265	$27.33	$27.35	$27.30
Purchase #4	$74.82	5.734%	$79.1102	$79.11	$79.10	$79.10
Purchase #5	$45.42	4.839%	$47.6179	$47.62	$47.60	$47.60
Purchase #6	$95.27	5.755%	$100.7528	$100.75	$100.75	$100.80
Purchase #7	$165.73	6.513%	$176.524	$176.52	$176.50	$176.50
7 purchase totals =	$679.32		$727.4816	$727.48	$727.45	$727.40