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	$59.88	3.429%	$61.9333	$61.93	$61.95	$61.90
Purchase #2	$202.84	6.119%	$215.2518	$215.25	$215.25	$215.30
Purchase #3	$65.37	5.128%	$68.7222	$68.72	$68.70	$68.70
Purchase #4	$43.88	10.579%	$48.5221	$48.52	$48.50	$48.50
Purchase #5	$30.47	7.549%	$32.7702	$32.77	$32.75	$32.80
Purchase #6	$93.78	13.639%	$106.5707	$106.57	$106.55	$106.60
Purchase #7	$121.90	5.470%	$128.5679	$128.57	$128.55	$128.60
7 purchase totals =	$618.12		$662.3382	$662.33	$662.25	$662.40