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	$136.38	4.563%	$142.603	$142.60	$142.60	$142.60
Purchase #2	$27.62	11.192%	$30.7112	$30.71	$30.70	$30.70
Purchase #3	$26.85	11.317%	$29.8886	$29.89	$29.90	$29.90
Purchase #4	$60.37	11.412%	$67.2594	$67.26	$67.25	$67.30
Purchase #5	$138.46	10.131%	$152.4874	$152.49	$152.50	$152.50
Purchase #6	$72.39	8.329%	$78.4194	$78.42	$78.40	$78.40
Purchase #7	$165.46	10.856%	$183.4223	$183.42	$183.40	$183.40
7 purchase totals =	$627.53		$684.7913	$684.79	$684.75	$684.80