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	$57.63	8.481%	$62.5176	$62.52	$62.50	$62.50
Purchase #2	$209.65	4.733%	$219.5727	$219.57	$219.55	$219.60
Purchase #3	$186.29	5.408%	$196.3646	$196.36	$196.35	$196.40
Purchase #4	$172.48	7.420%	$185.278	$185.28	$185.30	$185.30
Purchase #5	$19.58	5.826%	$20.7207	$20.72	$20.70	$20.70
Purchase #6	$174.78	10.271%	$192.7317	$192.73	$192.75	$192.70
Purchase #7	$208.78	11.433%	$232.6498	$232.65	$232.65	$232.60
7 purchase totals =	$1,029.19		$1,109.8351	$1,109.83	$1,109.80	$1,109.80