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	$150.38	11.301%	$167.3744	$167.37	$167.35	$167.40
Purchase #2	$198.81	5.595%	$209.9334	$209.93	$209.95	$209.90
Purchase #3	$150.74	11.709%	$168.3901	$168.39	$168.40	$168.40
Purchase #4	$111.60	13.819%	$127.022	$127.02	$127.00	$127.00
Purchase #5	$231.43	7.104%	$247.8708	$247.87	$247.85	$247.90
Purchase #6	$52.31	10.494%	$57.7994	$57.80	$57.80	$57.80
Purchase #7	$208.62	11.780%	$233.1954	$233.20	$233.20	$233.20
7 purchase totals =	$1,103.89		$1,211.5855	$1,211.58	$1,211.55	$1,211.60