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	$204.92	13.767%	$233.1313	$233.13	$233.15	$233.10
Purchase #2	$223.68	4.800%	$234.4166	$234.42	$234.40	$234.40
Purchase #3	$141.81	11.816%	$158.5663	$158.57	$158.55	$158.60
Purchase #4	$24.38	12.376%	$27.3973	$27.40	$27.40	$27.40
Purchase #5	$113.34	12.104%	$127.0587	$127.06	$127.05	$127.10
Purchase #6	$91.88	12.131%	$103.026	$103.03	$103.05	$103.00
Purchase #7	$239.58	9.444%	$262.2059	$262.21	$262.20	$262.20
7 purchase totals =	$1,039.59		$1,145.8021	$1,145.82	$1,145.80	$1,145.80