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	$163.52	12.846%	$184.5258	$184.53	$184.55	$184.50
Purchase #2	$162.58	6.201%	$172.6616	$172.66	$172.65	$172.70
Purchase #3	$186.68	12.261%	$209.5688	$209.57	$209.55	$209.60
Purchase #4	$40.97	11.252%	$45.5799	$45.58	$45.60	$45.60
Purchase #5	$62.90	4.684%	$65.8462	$65.85	$65.85	$65.80
Purchase #6	$127.80	5.338%	$134.622	$134.62	$134.60	$134.60
Purchase #7	$247.51	6.390%	$263.3259	$263.33	$263.35	$263.30
7 purchase totals =	$991.96		$1,076.1302	$1,076.14	$1,076.15	$1,076.10