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	$21.71	5.298%	$22.8602	$22.86	$22.85	$22.90
Purchase #2	$238.52	5.509%	$251.6601	$251.66	$251.65	$251.70
Purchase #3	$114.32	8.340%	$123.8543	$123.85	$123.85	$123.90
Purchase #4	$47.49	12.208%	$53.2876	$53.29	$53.30	$53.30
Purchase #5	$172.52	12.698%	$194.4266	$194.43	$194.45	$194.40
Purchase #6	$159.33	3.477%	$164.8699	$164.87	$164.85	$164.90
Purchase #7	$159.80	3.710%	$165.7286	$165.73	$165.75	$165.70
7 purchase totals =	$913.69		$976.6873	$976.69	$976.70	$976.80