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	$219.70	5.359%	$231.4737	$231.47	$231.45	$231.50
Purchase #2	$101.68	13.698%	$115.6081	$115.61	$115.60	$115.60
Purchase #3	$40.92	3.616%	$42.3997	$42.40	$42.40	$42.40
Purchase #4	$241.26	11.384%	$268.725	$268.73	$268.75	$268.70
Purchase #5	$112.89	12.715%	$127.244	$127.24	$127.25	$127.20
Purchase #6	$67.33	13.379%	$76.3381	$76.34	$76.35	$76.30
Purchase #7	$202.31	3.216%	$208.8163	$208.82	$208.80	$208.80
7 purchase totals =	$986.09		$1,070.6049	$1,070.61	$1,070.60	$1,070.50