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	$43.89	3.592%	$45.4665	$45.47	$45.45	$45.50
Purchase #2	$61.70	4.156%	$64.2643	$64.26	$64.25	$64.30
Purchase #3	$58.46	13.317%	$66.2451	$66.25	$66.25	$66.20
Purchase #4	$104.49	6.515%	$111.2975	$111.30	$111.30	$111.30
Purchase #5	$49.58	6.276%	$52.6916	$52.69	$52.70	$52.70
Purchase #6	$5.86	7.116%	$6.277	$6.28	$6.30	$6.30
Purchase #7	$49.58	8.330%	$53.71	$53.71	$53.70	$53.70
7 purchase totals =	$373.56		$399.9520	$399.96	$399.95	$400.00