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	$207.25	10.263%	$228.5201	$228.52	$228.50	$228.50
Purchase #2	$135.92	7.626%	$146.2853	$146.29	$146.30	$146.30
Purchase #3	$239.38	11.699%	$267.3851	$267.39	$267.40	$267.40
Purchase #4	$46.95	11.597%	$52.3948	$52.39	$52.40	$52.40
Purchase #5	$59.71	11.387%	$66.5092	$66.51	$66.50	$66.50
Purchase #6	$60.63	7.395%	$65.1136	$65.11	$65.10	$65.10
Purchase #7	$64.83	12.152%	$72.7081	$72.71	$72.70	$72.70
7 purchase totals =	$814.67		$898.9162	$898.92	$898.90	$898.90