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	$95.84	13.773%	$109.04	$109.04	$109.05	$109.00
Purchase #2	$154.90	11.483%	$172.6872	$172.69	$172.70	$172.70
Purchase #3	$103.70	10.120%	$114.1944	$114.19	$114.20	$114.20
Purchase #4	$226.86	7.373%	$243.5864	$243.59	$243.60	$243.60
Purchase #5	$194.32	5.731%	$205.4565	$205.46	$205.45	$205.50
Purchase #6	$42.51	7.730%	$45.796	$45.80	$45.80	$45.80
Purchase #7	$189.76	13.207%	$214.8216	$214.82	$214.80	$214.80
7 purchase totals =	$1,007.89		$1,105.5821	$1,105.59	$1,105.60	$1,105.60