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	$198.83	11.510%	$221.7153	$221.72	$221.70	$221.70
Purchase #2	$26.55	11.110%	$29.4997	$29.50	$29.50	$29.50
Purchase #3	$183.99	8.514%	$199.6549	$199.65	$199.65	$199.70
Purchase #4	$93.28	10.497%	$103.0716	$103.07	$103.05	$103.10
Purchase #5	$163.38	11.713%	$182.5167	$182.52	$182.50	$182.50
Purchase #6	$118.73	13.300%	$134.5211	$134.52	$134.50	$134.50
Purchase #7	$178.38	5.682%	$188.5156	$188.52	$188.50	$188.50
7 purchase totals =	$963.14		$1,059.4949	$1,059.50	$1,059.40	$1,059.50