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	$51.25	8.361%	$55.535	$55.54	$55.55	$55.50
Purchase #2	$19.43	7.323%	$20.8529	$20.85	$20.85	$20.90
Purchase #3	$29.91	7.543%	$32.1661	$32.17	$32.15	$32.20
Purchase #4	$87.28	9.710%	$95.7549	$95.75	$95.75	$95.80
Purchase #5	$7.93	11.635%	$8.8527	$8.85	$8.85	$8.90
Purchase #6	$5.78	10.570%	$6.3909	$6.39	$6.40	$6.40
Purchase #7	$186.84	5.388%	$196.9069	$196.91	$196.90	$196.90
7 purchase totals =	$388.42		$416.4594	$416.46	$416.45	$416.60