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	$103.87	4.320%	$108.3572	$108.36	$108.35	$108.40
Purchase #2	$57.52	3.391%	$59.4705	$59.47	$59.45	$59.50
Purchase #3	$52.52	4.148%	$54.6985	$54.70	$54.70	$54.70
Purchase #4	$224.35	10.766%	$248.5035	$248.50	$248.50	$248.50
Purchase #5	$217.26	4.556%	$227.1584	$227.16	$227.15	$227.20
Purchase #6	$77.50	13.527%	$87.9834	$87.98	$88.00	$88.00
Purchase #7	$141.33	6.688%	$150.7822	$150.78	$150.80	$150.80
7 purchase totals =	$874.35		$936.9537	$936.95	$936.95	$937.10