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	$206.76	6.537%	$220.2759	$220.28	$220.30	$220.30
Purchase #2	$249.36	9.577%	$273.2412	$273.24	$273.25	$273.20
Purchase #3	$168.32	8.443%	$182.5313	$182.53	$182.55	$182.50
Purchase #4	$241.79	12.240%	$271.3851	$271.39	$271.40	$271.40
Purchase #5	$48.67	9.207%	$53.151	$53.15	$53.15	$53.20
Purchase #6	$50.67	7.461%	$54.4505	$54.45	$54.45	$54.50
Purchase #7	$116.99	5.574%	$123.511	$123.51	$123.50	$123.50
7 purchase totals =	$1,082.56		$1,178.5460	$1,178.55	$1,178.60	$1,178.60