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	$128.47	11.707%	$143.51	$143.51	$143.50	$143.50
Purchase #2	$125.30	13.654%	$142.4085	$142.41	$142.40	$142.40
Purchase #3	$219.85	4.751%	$230.2951	$230.30	$230.30	$230.30
Purchase #4	$242.94	13.827%	$276.5313	$276.53	$276.55	$276.50
Purchase #5	$103.58	7.542%	$111.392	$111.39	$111.40	$111.40
Purchase #6	$197.39	8.780%	$214.7208	$214.72	$214.70	$214.70
Purchase #7	$182.80	12.199%	$205.0998	$205.10	$205.10	$205.10
7 purchase totals =	$1,200.33		$1,323.9575	$1,323.96	$1,323.95	$1,323.90