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	$32.68	5.303%	$34.413	$34.41	$34.40	$34.40
Purchase #2	$205.45	9.768%	$225.5184	$225.52	$225.50	$225.50
Purchase #3	$76.26	4.254%	$79.5041	$79.50	$79.50	$79.50
Purchase #4	$64.71	12.526%	$72.8156	$72.82	$72.80	$72.80
Purchase #5	$236.32	11.224%	$262.8446	$262.84	$262.85	$262.80
Purchase #6	$34.40	9.841%	$37.7853	$37.79	$37.80	$37.80
Purchase #7	$141.76	7.102%	$151.8278	$151.83	$151.85	$151.80
7 purchase totals =	$791.58		$864.7088	$864.71	$864.70	$864.60