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	$115.67	9.435%	$126.5835	$126.58	$126.60	$126.60
Purchase #2	$158.74	9.310%	$173.5187	$173.52	$173.50	$173.50
Purchase #3	$110.83	11.832%	$123.9434	$123.94	$123.95	$123.90
Purchase #4	$129.41	10.122%	$142.5089	$142.51	$142.50	$142.50
Purchase #5	$223.46	8.442%	$242.3245	$242.32	$242.30	$242.30
Purchase #6	$41.94	4.816%	$43.9598	$43.96	$43.95	$44.00
Purchase #7	$130.49	4.431%	$136.272	$136.27	$136.25	$136.30
7 purchase totals =	$910.54		$989.1108	$989.10	$989.05	$989.10