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	$78.26	10.426%	$86.4194	$86.42	$86.40	$86.40
Purchase #2	$43.83	6.156%	$46.5282	$46.53	$46.55	$46.50
Purchase #3	$53.77	12.589%	$60.5391	$60.54	$60.55	$60.50
Purchase #4	$164.94	5.637%	$174.2377	$174.24	$174.25	$174.20
Purchase #5	$81.97	11.189%	$91.1416	$91.14	$91.15	$91.10
Purchase #6	$88.28	4.794%	$92.5121	$92.51	$92.50	$92.50
Purchase #7	$104.56	8.488%	$113.4351	$113.44	$113.45	$113.40
7 purchase totals =	$615.61		$664.8132	$664.82	$664.85	$664.60