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	$96.47	12.816%	$108.8336	$108.83	$108.85	$108.80
Purchase #2	$68.83	12.231%	$77.2486	$77.25	$77.25	$77.20
Purchase #3	$11.66	4.182%	$12.1476	$12.15	$12.15	$12.10
Purchase #4	$62.95	13.393%	$71.3809	$71.38	$71.40	$71.40
Purchase #5	$75.70	6.647%	$80.7318	$80.73	$80.75	$80.70
Purchase #6	$228.37	6.194%	$242.5152	$242.52	$242.50	$242.50
Purchase #7	$235.78	13.504%	$267.6197	$267.62	$267.60	$267.60
7 purchase totals =	$779.76		$860.4774	$860.48	$860.50	$860.30