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	$188.75	9.626%	$206.9191	$206.92	$206.90	$206.90
Purchase #2	$132.56	7.539%	$142.5537	$142.55	$142.55	$142.60
Purchase #3	$66.39	7.840%	$71.595	$71.60	$71.60	$71.60
Purchase #4	$158.96	8.273%	$172.1108	$172.11	$172.10	$172.10
Purchase #5	$41.33	6.494%	$44.014	$44.01	$44.00	$44.00
Purchase #6	$117.70	8.354%	$127.5327	$127.53	$127.55	$127.50
Purchase #7	$14.25	10.234%	$15.7083	$15.71	$15.70	$15.70
7 purchase totals =	$719.94		$780.4336	$780.43	$780.40	$780.40