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	$199.89	8.577%	$217.0346	$217.03	$217.05	$217.00
Purchase #2	$27.37	13.820%	$31.1525	$31.15	$31.15	$31.20
Purchase #3	$158.69	9.111%	$173.1482	$173.15	$173.15	$173.10
Purchase #4	$37.60	5.592%	$39.7026	$39.70	$39.70	$39.70
Purchase #5	$231.56	11.617%	$258.4603	$258.46	$258.45	$258.50
Purchase #6	$86.37	7.455%	$92.8089	$92.81	$92.80	$92.80
Purchase #7	$82.72	6.516%	$88.11	$88.11	$88.10	$88.10
7 purchase totals =	$824.20		$900.4171	$900.41	$900.40	$900.40