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	$47.38	8.705%	$51.5044	$51.50	$51.50	$51.50
Purchase #2	$13.94	3.230%	$14.3903	$14.39	$14.40	$14.40
Purchase #3	$53.36	12.491%	$60.0252	$60.03	$60.05	$60.00
Purchase #4	$86.74	4.408%	$90.5635	$90.56	$90.55	$90.60
Purchase #5	$43.72	11.749%	$48.8567	$48.86	$48.85	$48.90
Purchase #6	$155.25	9.172%	$169.4895	$169.49	$169.50	$169.50
Purchase #7	$19.83	11.620%	$22.1342	$22.13	$22.15	$22.10
7 purchase totals =	$420.22		$456.9638	$456.96	$457.00	$457.00