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	$134.25	12.406%	$150.9051	$150.91	$150.90	$150.90
Purchase #2	$144.38	5.166%	$151.8387	$151.84	$151.85	$151.80
Purchase #3	$168.32	13.637%	$191.2738	$191.27	$191.25	$191.30
Purchase #4	$21.81	12.731%	$24.5866	$24.59	$24.60	$24.60
Purchase #5	$160.70	5.553%	$169.6237	$169.62	$169.60	$169.60
Purchase #6	$159.50	4.848%	$167.2326	$167.23	$167.25	$167.20
Purchase #7	$119.54	5.715%	$126.3717	$126.37	$126.35	$126.40
7 purchase totals =	$908.50		$981.8322	$981.83	$981.80	$981.80