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	$153.46	9.695%	$168.3379	$168.34	$168.35	$168.30
Purchase #2	$157.59	9.611%	$172.736	$172.74	$172.75	$172.70
Purchase #3	$102.64	11.494%	$114.4374	$114.44	$114.45	$114.40
Purchase #4	$67.87	4.718%	$71.0721	$71.07	$71.05	$71.10
Purchase #5	$101.80	9.532%	$111.5036	$111.50	$111.50	$111.50
Purchase #6	$243.39	11.826%	$272.1733	$272.17	$272.15	$272.20
Purchase #7	$78.74	4.714%	$82.4518	$82.45	$82.45	$82.50
7 purchase totals =	$905.49		$992.7121	$992.71	$992.70	$992.70