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	$195.30	6.849%	$208.6761	$208.68	$208.70	$208.70
Purchase #2	$84.90	6.292%	$90.2419	$90.24	$90.25	$90.20
Purchase #3	$119.74	3.230%	$123.6076	$123.61	$123.60	$123.60
Purchase #4	$95.25	3.763%	$98.8343	$98.83	$98.85	$98.80
Purchase #5	$174.37	13.689%	$198.2395	$198.24	$198.25	$198.20
Purchase #6	$232.86	12.112%	$261.064	$261.06	$261.05	$261.10
Purchase #7	$238.80	9.786%	$262.169	$262.17	$262.15	$262.20
7 purchase totals =	$1,141.22		$1,242.8324	$1,242.83	$1,242.85	$1,242.80