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	$88.51	7.108%	$94.8013	$94.80	$94.80	$94.80
Purchase #2	$132.81	6.291%	$141.1651	$141.17	$141.15	$141.20
Purchase #3	$111.59	5.457%	$117.6795	$117.68	$117.70	$117.70
Purchase #4	$44.67	5.436%	$47.0983	$47.10	$47.10	$47.10
Purchase #5	$169.33	9.290%	$185.0608	$185.06	$185.05	$185.10
Purchase #6	$81.26	5.184%	$85.4725	$85.47	$85.45	$85.50
Purchase #7	$85.89	10.487%	$94.8973	$94.90	$94.90	$94.90
7 purchase totals =	$714.06		$766.1748	$766.18	$766.15	$766.30