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	$52.60	12.657%	$59.2576	$59.26	$59.25	$59.30
Purchase #2	$211.41	5.185%	$222.3716	$222.37	$222.35	$222.40
Purchase #3	$93.99	12.733%	$105.9577	$105.96	$105.95	$106.00
Purchase #4	$39.49	7.411%	$42.4166	$42.42	$42.40	$42.40
Purchase #5	$132.61	5.405%	$139.7776	$139.78	$139.80	$139.80
Purchase #6	$101.62	12.812%	$114.6396	$114.64	$114.65	$114.60
Purchase #7	$206.36	6.641%	$220.0644	$220.06	$220.05	$220.10
7 purchase totals =	$838.08		$904.4851	$904.49	$904.45	$904.60