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	$104.31	6.541%	$111.1329	$111.13	$111.15	$111.10
Purchase #2	$103.32	4.440%	$107.9074	$107.91	$107.90	$107.90
Purchase #3	$10.92	13.826%	$12.4298	$12.43	$12.45	$12.40
Purchase #4	$169.93	7.581%	$182.8124	$182.81	$182.80	$182.80
Purchase #5	$115.98	11.257%	$129.0359	$129.04	$129.05	$129.00
Purchase #6	$166.80	4.685%	$174.6146	$174.61	$174.60	$174.60
Purchase #7	$133.72	12.264%	$150.1194	$150.12	$150.10	$150.10
7 purchase totals =	$804.98		$868.0524	$868.05	$868.05	$867.90