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	$73.61	8.461%	$79.8381	$79.84	$79.85	$79.80
Purchase #2	$68.31	7.127%	$73.1785	$73.18	$73.20	$73.20
Purchase #3	$177.92	10.215%	$196.0945	$196.09	$196.10	$196.10
Purchase #4	$106.39	12.735%	$119.9388	$119.94	$119.95	$119.90
Purchase #5	$159.88	4.789%	$167.5367	$167.54	$167.55	$167.50
Purchase #6	$188.28	6.301%	$200.1435	$200.14	$200.15	$200.10
Purchase #7	$233.57	10.130%	$257.2306	$257.23	$257.25	$257.20
7 purchase totals =	$1,007.96		$1,093.9607	$1,093.96	$1,094.05	$1,093.80