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	$224.27	3.795%	$232.781	$232.78	$232.80	$232.80
Purchase #2	$144.77	12.405%	$162.7287	$162.73	$162.75	$162.70
Purchase #3	$64.47	3.583%	$66.78	$66.78	$66.80	$66.80
Purchase #4	$230.83	9.128%	$251.9002	$251.90	$251.90	$251.90
Purchase #5	$36.83	9.872%	$40.4659	$40.47	$40.45	$40.50
Purchase #6	$173.36	10.536%	$191.6252	$191.63	$191.65	$191.60
Purchase #7	$189.74	9.792%	$208.3193	$208.32	$208.30	$208.30
7 purchase totals =	$1,064.27		$1,154.6003	$1,154.61	$1,154.65	$1,154.60