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	$82.25	4.649%	$86.0738	$86.07	$86.05	$86.10
Purchase #2	$228.56	6.640%	$243.7364	$243.74	$243.75	$243.70
Purchase #3	$116.85	9.793%	$128.2931	$128.29	$128.30	$128.30
Purchase #4	$103.70	7.560%	$111.5397	$111.54	$111.55	$111.50
Purchase #5	$154.83	7.682%	$166.724	$166.72	$166.70	$166.70
Purchase #6	$73.38	11.723%	$81.9823	$81.98	$82.00	$82.00
Purchase #7	$9.45	10.515%	$10.4437	$10.44	$10.45	$10.40
7 purchase totals =	$769.02		$828.7930	$828.78	$828.80	$828.70