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	$196.40	13.177%	$222.2796	$222.28	$222.30	$222.30
Purchase #2	$51.71	6.129%	$54.8793	$54.88	$54.90	$54.90
Purchase #3	$11.83	11.289%	$13.1655	$13.17	$13.15	$13.20
Purchase #4	$235.71	3.417%	$243.7642	$243.76	$243.75	$243.80
Purchase #5	$92.81	12.649%	$104.5495	$104.55	$104.55	$104.50
Purchase #6	$230.63	7.235%	$247.3161	$247.32	$247.30	$247.30
Purchase #7	$180.38	10.559%	$199.4263	$199.43	$199.45	$199.40
7 purchase totals =	$999.47		$1,085.3805	$1,085.39	$1,085.40	$1,085.40