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	$104.88	6.394%	$111.586	$111.59	$111.60	$111.60
Purchase #2	$76.77	13.423%	$87.0748	$87.07	$87.05	$87.10
Purchase #3	$249.75	9.412%	$273.2565	$273.26	$273.25	$273.30
Purchase #4	$15.49	13.666%	$17.6069	$17.61	$17.60	$17.60
Purchase #5	$111.75	13.608%	$126.9569	$126.96	$126.95	$127.00
Purchase #6	$163.86	13.351%	$185.7369	$185.74	$185.75	$185.70
Purchase #7	$199.92	7.820%	$215.5537	$215.55	$215.55	$215.60
7 purchase totals =	$922.42		$1,017.7717	$1,017.78	$1,017.75	$1,017.90