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	$149.25	10.209%	$164.4869	$164.49	$164.50	$164.50
Purchase #2	$48.42	9.175%	$52.8625	$52.86	$52.85	$52.90
Purchase #3	$152.49	3.861%	$158.3776	$158.38	$158.40	$158.40
Purchase #4	$123.61	12.281%	$138.7905	$138.79	$138.80	$138.80
Purchase #5	$85.38	7.201%	$91.5282	$91.53	$91.55	$91.50
Purchase #6	$128.83	6.626%	$137.3663	$137.37	$137.35	$137.40
Purchase #7	$85.73	3.729%	$88.9269	$88.93	$88.95	$88.90
7 purchase totals =	$773.71		$832.3389	$832.35	$832.40	$832.40