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	$56.89	4.398%	$59.392	$59.39	$59.40	$59.40
Purchase #2	$216.45	13.409%	$245.4738	$245.47	$245.45	$245.50
Purchase #3	$151.65	5.394%	$159.83	$159.83	$159.85	$159.80
Purchase #4	$90.77	10.265%	$100.0875	$100.09	$100.10	$100.10
Purchase #5	$46.35	10.866%	$51.3864	$51.39	$51.40	$51.40
Purchase #6	$238.73	4.693%	$249.9336	$249.93	$249.95	$249.90
Purchase #7	$212.48	7.441%	$228.2906	$228.29	$228.30	$228.30
7 purchase totals =	$1,013.32		$1,094.3939	$1,094.39	$1,094.45	$1,094.40