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	$57.30	5.219%	$60.2905	$60.29	$60.30	$60.30
Purchase #2	$151.55	7.493%	$162.9056	$162.91	$162.90	$162.90
Purchase #3	$169.34	6.647%	$180.596	$180.60	$180.60	$180.60
Purchase #4	$74.32	12.225%	$83.4056	$83.41	$83.40	$83.40
Purchase #5	$101.28	9.683%	$111.0869	$111.09	$111.10	$111.10
Purchase #6	$65.42	3.653%	$67.8098	$67.81	$67.80	$67.80
Purchase #7	$238.61	6.643%	$254.4609	$254.46	$254.45	$254.50
7 purchase totals =	$857.82		$920.5553	$920.57	$920.55	$920.60