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	$110.72	5.811%	$117.1539	$117.15	$117.15	$117.20
Purchase #2	$123.89	13.380%	$140.4665	$140.47	$140.45	$140.50
Purchase #3	$191.89	12.865%	$216.5766	$216.58	$216.60	$216.60
Purchase #4	$23.32	4.103%	$24.2768	$24.28	$24.30	$24.30
Purchase #5	$37.47	9.513%	$41.0345	$41.03	$41.05	$41.00
Purchase #6	$215.58	12.457%	$242.4348	$242.43	$242.45	$242.40
Purchase #7	$11.56	8.441%	$12.5358	$12.54	$12.55	$12.50
7 purchase totals =	$714.43		$794.4789	$794.48	$794.55	$794.50