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	$77.75	4.801%	$81.4828	$81.48	$81.50	$81.50
Purchase #2	$22.61	5.512%	$23.8563	$23.86	$23.85	$23.90
Purchase #3	$156.64	11.415%	$174.5205	$174.52	$174.50	$174.50
Purchase #4	$213.98	11.588%	$238.776	$238.78	$238.80	$238.80
Purchase #5	$42.89	12.183%	$48.1153	$48.12	$48.10	$48.10
Purchase #6	$39.29	9.519%	$43.03	$43.03	$43.05	$43.00
Purchase #7	$13.61	6.118%	$14.4427	$14.44	$14.45	$14.40
7 purchase totals =	$566.77		$624.2236	$624.23	$624.25	$624.20