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	$153.85	11.763%	$171.9474	$171.95	$171.95	$171.90
Purchase #2	$90.46	12.164%	$101.4636	$101.46	$101.45	$101.50
Purchase #3	$41.47	11.285%	$46.1499	$46.15	$46.15	$46.10
Purchase #4	$32.73	11.305%	$36.4301	$36.43	$36.45	$36.40
Purchase #5	$121.93	11.553%	$136.0166	$136.02	$136.00	$136.00
Purchase #6	$23.89	7.139%	$25.5955	$25.60	$25.60	$25.60
Purchase #7	$57.39	6.307%	$61.0096	$61.01	$61.00	$61.00
7 purchase totals =	$521.72		$578.6127	$578.62	$578.60	$578.50