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	$178.41	4.352%	$186.1744	$186.17	$186.15	$186.20
Purchase #2	$223.75	6.491%	$238.2736	$238.27	$238.25	$238.30
Purchase #3	$17.46	5.796%	$18.472	$18.47	$18.45	$18.50
Purchase #4	$197.38	8.568%	$214.2915	$214.29	$214.30	$214.30
Purchase #5	$51.48	3.348%	$53.2036	$53.20	$53.20	$53.20
Purchase #6	$220.90	5.753%	$233.6084	$233.61	$233.60	$233.60
Purchase #7	$218.55	10.649%	$241.8234	$241.82	$241.80	$241.80
7 purchase totals =	$1,107.93		$1,185.8469	$1,185.83	$1,185.75	$1,185.90