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	$100.45	13.873%	$114.3854	$114.39	$114.40	$114.40
Purchase #2	$67.82	11.609%	$75.6932	$75.69	$75.70	$75.70
Purchase #3	$205.92	3.364%	$212.8471	$212.85	$212.85	$212.80
Purchase #4	$146.35	12.589%	$164.774	$164.77	$164.75	$164.80
Purchase #5	$214.50	3.631%	$222.2885	$222.29	$222.30	$222.30
Purchase #6	$166.59	3.154%	$171.8442	$171.84	$171.85	$171.80
Purchase #7	$193.28	13.183%	$218.7601	$218.76	$218.75	$218.80
7 purchase totals =	$1,094.91		$1,180.5925	$1,180.59	$1,180.60	$1,180.60