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	$136.64	13.231%	$154.7188	$154.72	$154.70	$154.70
Purchase #2	$195.27	11.427%	$217.5835	$217.58	$217.60	$217.60
Purchase #3	$42.62	6.645%	$45.4521	$45.45	$45.45	$45.50
Purchase #4	$80.45	12.490%	$90.4982	$90.50	$90.50	$90.50
Purchase #5	$103.37	3.676%	$107.1699	$107.17	$107.15	$107.20
Purchase #6	$143.46	9.592%	$157.2207	$157.22	$157.20	$157.20
Purchase #7	$191.56	10.287%	$211.2658	$211.27	$211.25	$211.30
7 purchase totals =	$893.37		$983.9090	$983.91	$983.85	$984.00