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	$99.61	12.366%	$111.9278	$111.93	$111.95	$111.90
Purchase #2	$150.70	10.235%	$166.1241	$166.12	$166.10	$166.10
Purchase #3	$60.88	7.493%	$65.4417	$65.44	$65.45	$65.40
Purchase #4	$95.89	12.777%	$108.1419	$108.14	$108.15	$108.10
Purchase #5	$117.26	3.869%	$121.7968	$121.80	$121.80	$121.80
Purchase #6	$125.41	13.666%	$142.5485	$142.55	$142.55	$142.50
Purchase #7	$164.46	12.333%	$184.7429	$184.74	$184.75	$184.70
7 purchase totals =	$814.21		$900.7237	$900.72	$900.75	$900.50