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	$213.91	10.523%	$236.4197	$236.42	$236.40	$236.40
Purchase #2	$113.81	12.611%	$128.1626	$128.16	$128.15	$128.20
Purchase #3	$90.36	11.701%	$100.933	$100.93	$100.95	$100.90
Purchase #4	$236.78	7.617%	$254.8155	$254.82	$254.80	$254.80
Purchase #5	$112.35	13.570%	$127.5959	$127.60	$127.60	$127.60
Purchase #6	$67.45	12.652%	$75.9838	$75.98	$76.00	$76.00
Purchase #7	$212.39	7.170%	$227.6184	$227.62	$227.60	$227.60
7 purchase totals =	$1,047.05		$1,151.5289	$1,151.53	$1,151.50	$1,151.50