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	$242.90	9.616%	$266.2573	$266.26	$266.25	$266.30
Purchase #2	$107.72	3.198%	$111.1649	$111.16	$111.15	$111.20
Purchase #3	$150.55	7.301%	$161.5417	$161.54	$161.55	$161.50
Purchase #4	$12.26	8.649%	$13.3204	$13.32	$13.30	$13.30
Purchase #5	$219.90	6.210%	$233.5558	$233.56	$233.55	$233.60
Purchase #6	$207.25	9.626%	$227.1999	$227.20	$227.20	$227.20
Purchase #7	$82.50	11.726%	$92.174	$92.17	$92.15	$92.20
7 purchase totals =	$1,023.08		$1,105.2140	$1,105.21	$1,105.15	$1,105.30