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	$242.74	8.824%	$264.1594	$264.16	$264.15	$264.20
Purchase #2	$60.64	9.749%	$66.5518	$66.55	$66.55	$66.60
Purchase #3	$115.96	6.395%	$123.3756	$123.38	$123.40	$123.40
Purchase #4	$137.53	3.589%	$142.466	$142.47	$142.45	$142.50
Purchase #5	$170.66	5.758%	$180.4866	$180.49	$180.50	$180.50
Purchase #6	$20.88	7.267%	$22.3973	$22.40	$22.40	$22.40
Purchase #7	$233.80	10.658%	$258.7184	$258.72	$258.70	$258.70
7 purchase totals =	$982.21		$1,058.1551	$1,058.17	$1,058.15	$1,058.30