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	$102.61	8.546%	$111.3791	$111.38	$111.40	$111.40
Purchase #2	$233.44	4.722%	$244.463	$244.46	$244.45	$244.50
Purchase #3	$40.66	11.829%	$45.4697	$45.47	$45.45	$45.50
Purchase #4	$193.94	3.537%	$200.7997	$200.80	$200.80	$200.80
Purchase #5	$195.58	4.851%	$205.0676	$205.07	$205.05	$205.10
Purchase #6	$19.89	8.326%	$21.546	$21.55	$21.55	$21.50
Purchase #7	$188.70	7.129%	$202.1524	$202.15	$202.15	$202.20
7 purchase totals =	$974.82		$1,030.8775	$1,030.88	$1,030.85	$1,031.00