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	$104.93	6.153%	$111.3863	$111.39	$111.40	$111.40
Purchase #2	$222.82	3.356%	$230.2978	$230.30	$230.30	$230.30
Purchase #3	$170.48	8.678%	$185.2743	$185.27	$185.25	$185.30
Purchase #4	$38.88	6.803%	$41.525	$41.53	$41.55	$41.50
Purchase #5	$149.84	3.718%	$155.4111	$155.41	$155.40	$155.40
Purchase #6	$126.80	10.674%	$140.3346	$140.33	$140.35	$140.30
Purchase #7	$184.40	7.161%	$197.6049	$197.60	$197.60	$197.60
7 purchase totals =	$998.15		$1,061.8340	$1,061.83	$1,061.85	$1,061.80