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	$208.96	13.558%	$237.2908	$237.29	$237.30	$237.30
Purchase #2	$108.95	4.869%	$114.2548	$114.25	$114.25	$114.30
Purchase #3	$26.71	6.713%	$28.503	$28.50	$28.50	$28.50
Purchase #4	$138.58	12.364%	$155.714	$155.71	$155.70	$155.70
Purchase #5	$39.61	7.610%	$42.6243	$42.62	$42.60	$42.60
Purchase #6	$68.89	12.205%	$77.298	$77.30	$77.30	$77.30
Purchase #7	$81.32	10.249%	$89.6545	$89.65	$89.65	$89.70
7 purchase totals =	$673.02		$745.3394	$745.32	$745.30	$745.40