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	$62.29	6.173%	$66.1352	$66.14	$66.15	$66.10
Purchase #2	$159.80	5.437%	$168.4883	$168.49	$168.50	$168.50
Purchase #3	$123.39	13.318%	$139.8231	$139.82	$139.80	$139.80
Purchase #4	$184.63	11.315%	$205.5209	$205.52	$205.50	$205.50
Purchase #5	$244.35	10.629%	$270.322	$270.32	$270.30	$270.30
Purchase #6	$63.44	6.411%	$67.5071	$67.51	$67.50	$67.50
Purchase #7	$121.78	5.620%	$128.624	$128.62	$128.60	$128.60
7 purchase totals =	$959.68		$1,046.4206	$1,046.42	$1,046.35	$1,046.30