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	$211.26	3.467%	$218.5844	$218.58	$218.60	$218.60
Purchase #2	$32.30	5.610%	$34.112	$34.11	$34.10	$34.10
Purchase #3	$119.69	6.709%	$127.72	$127.72	$127.70	$127.70
Purchase #4	$31.27	6.292%	$33.2375	$33.24	$33.25	$33.20
Purchase #5	$132.73	7.491%	$142.6728	$142.67	$142.65	$142.70
Purchase #6	$126.94	3.777%	$131.7345	$131.73	$131.75	$131.70
Purchase #7	$232.68	10.311%	$256.6716	$256.67	$256.65	$256.70
7 purchase totals =	$886.87		$944.7328	$944.72	$944.70	$944.70