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	$109.81	8.617%	$119.2723	$119.27	$119.25	$119.30
Purchase #2	$136.74	4.353%	$142.6923	$142.69	$142.70	$142.70
Purchase #3	$241.26	13.454%	$273.7191	$273.72	$273.70	$273.70
Purchase #4	$231.65	13.578%	$263.1034	$263.10	$263.10	$263.10
Purchase #5	$105.73	5.372%	$111.4098	$111.41	$111.40	$111.40
Purchase #6	$129.55	3.306%	$133.8329	$133.83	$133.85	$133.80
Purchase #7	$56.28	11.221%	$62.5952	$62.60	$62.60	$62.60
7 purchase totals =	$1,011.02		$1,106.6250	$1,106.62	$1,106.60	$1,106.60