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	$14.26	4.658%	$14.9242	$14.92	$14.90	$14.90
Purchase #2	$199.28	8.428%	$216.0753	$216.08	$216.10	$216.10
Purchase #3	$204.87	3.395%	$211.8253	$211.83	$211.85	$211.80
Purchase #4	$86.82	3.770%	$90.0931	$90.09	$90.10	$90.10
Purchase #5	$127.42	3.179%	$131.4707	$131.47	$131.45	$131.50
Purchase #6	$163.43	12.858%	$184.4438	$184.44	$184.45	$184.40
Purchase #7	$210.43	4.471%	$219.8383	$219.84	$219.85	$219.80
7 purchase totals =	$1,006.51		$1,068.6707	$1,068.67	$1,068.70	$1,068.60