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	$155.58	11.774%	$173.898	$173.90	$173.90	$173.90
Purchase #2	$226.67	11.220%	$252.1024	$252.10	$252.10	$252.10
Purchase #3	$107.72	6.118%	$114.3103	$114.31	$114.30	$114.30
Purchase #4	$43.63	5.253%	$45.9219	$45.92	$45.90	$45.90
Purchase #5	$126.69	8.742%	$137.7652	$137.77	$137.75	$137.80
Purchase #6	$137.47	4.332%	$143.4252	$143.43	$143.45	$143.40
Purchase #7	$212.86	5.264%	$224.065	$224.07	$224.05	$224.10
7 purchase totals =	$1,010.62		$1,091.4880	$1,091.50	$1,091.45	$1,091.50