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	$39.50	4.795%	$41.394	$41.39	$41.40	$41.40
Purchase #2	$241.83	4.153%	$251.8732	$251.87	$251.85	$251.90
Purchase #3	$211.59	5.198%	$222.5884	$222.59	$222.60	$222.60
Purchase #4	$247.61	3.469%	$256.1996	$256.20	$256.20	$256.20
Purchase #5	$82.80	8.696%	$90.0003	$90.00	$90.00	$90.00
Purchase #6	$52.60	7.137%	$56.3541	$56.35	$56.35	$56.40
Purchase #7	$240.62	4.222%	$250.779	$250.78	$250.80	$250.80
7 purchase totals =	$1,116.55		$1,169.1886	$1,169.18	$1,169.20	$1,169.30