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	$196.85	10.760%	$218.0311	$218.03	$218.05	$218.00
Purchase #2	$250.30	4.274%	$260.9978	$261.00	$261.00	$261.00
Purchase #3	$41.30	3.147%	$42.5997	$42.60	$42.60	$42.60
Purchase #4	$59.84	12.375%	$67.2452	$67.25	$67.25	$67.20
Purchase #5	$228.45	8.397%	$247.6329	$247.63	$247.65	$247.60
Purchase #6	$128.80	7.403%	$138.3351	$138.34	$138.35	$138.30
Purchase #7	$96.52	13.483%	$109.5338	$109.53	$109.55	$109.50
7 purchase totals =	$1,002.06		$1,084.3756	$1,084.38	$1,084.45	$1,084.20