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	$171.86	11.846%	$192.2185	$192.22	$192.20	$192.20
Purchase #2	$177.57	9.189%	$193.8869	$193.89	$193.90	$193.90
Purchase #3	$197.71	8.687%	$214.8851	$214.89	$214.90	$214.90
Purchase #4	$82.73	9.274%	$90.4024	$90.40	$90.40	$90.40
Purchase #5	$38.33	12.399%	$43.0825	$43.08	$43.10	$43.10
Purchase #6	$234.30	7.224%	$251.2258	$251.23	$251.25	$251.20
Purchase #7	$173.45	5.438%	$182.8822	$182.88	$182.90	$182.90
7 purchase totals =	$1,075.95		$1,168.5834	$1,168.59	$1,168.65	$1,168.60