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	$193.45	6.155%	$205.3568	$205.36	$205.35	$205.40
Purchase #2	$56.65	7.249%	$60.7566	$60.76	$60.75	$60.80
Purchase #3	$43.39	9.562%	$47.539	$47.54	$47.55	$47.50
Purchase #4	$36.89	12.404%	$41.4658	$41.47	$41.45	$41.50
Purchase #5	$193.76	11.168%	$215.3991	$215.40	$215.40	$215.40
Purchase #6	$25.46	7.592%	$27.3929	$27.39	$27.40	$27.40
Purchase #7	$111.95	13.476%	$127.0364	$127.04	$127.05	$127.00
7 purchase totals =	$661.55		$724.9466	$724.96	$724.95	$725.00