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	$13.93	9.575%	$15.2638	$15.26	$15.25	$15.30
Purchase #2	$223.78	9.395%	$244.8041	$244.80	$244.80	$244.80
Purchase #3	$82.67	9.519%	$90.5394	$90.54	$90.55	$90.50
Purchase #4	$131.89	13.387%	$149.5461	$149.55	$149.55	$149.50
Purchase #5	$210.96	9.105%	$230.1679	$230.17	$230.15	$230.20
Purchase #6	$87.67	5.677%	$92.647	$92.65	$92.65	$92.60
Purchase #7	$168.52	12.712%	$189.9423	$189.94	$189.95	$189.90
7 purchase totals =	$919.42		$1,012.9106	$1,012.91	$1,012.90	$1,012.80