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	$132.39	6.323%	$140.761	$140.76	$140.75	$140.80
Purchase #2	$25.31	7.464%	$27.1991	$27.20	$27.20	$27.20
Purchase #3	$115.33	7.181%	$123.6118	$123.61	$123.60	$123.60
Purchase #4	$171.41	10.872%	$190.0457	$190.05	$190.05	$190.00
Purchase #5	$89.63	9.617%	$98.2497	$98.25	$98.25	$98.20
Purchase #6	$128.28	3.426%	$132.6749	$132.67	$132.65	$132.70
Purchase #7	$133.67	13.447%	$151.6446	$151.64	$151.65	$151.60
7 purchase totals =	$796.02		$864.1868	$864.18	$864.15	$864.10