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	$129.90	9.722%	$142.5289	$142.53	$142.55	$142.50
Purchase #2	$48.77	6.344%	$51.864	$51.86	$51.85	$51.90
Purchase #3	$12.70	12.114%	$14.2385	$14.24	$14.25	$14.20
Purchase #4	$116.30	12.786%	$131.1701	$131.17	$131.15	$131.20
Purchase #5	$39.67	13.668%	$45.0921	$45.09	$45.10	$45.10
Purchase #6	$144.79	10.706%	$160.2912	$160.29	$160.30	$160.30
Purchase #7	$34.91	11.454%	$38.9086	$38.91	$38.90	$38.90
7 purchase totals =	$527.04		$584.0934	$584.09	$584.10	$584.10