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	$14.36	5.819%	$15.1956	$15.20	$15.20	$15.20
Purchase #2	$114.37	11.270%	$127.2595	$127.26	$127.25	$127.30
Purchase #3	$162.81	12.376%	$182.9594	$182.96	$182.95	$183.00
Purchase #4	$160.95	9.301%	$175.92	$175.92	$175.90	$175.90
Purchase #5	$249.30	9.352%	$272.6145	$272.61	$272.60	$272.60
Purchase #6	$137.46	10.151%	$151.4136	$151.41	$151.40	$151.40
Purchase #7	$71.71	7.685%	$77.2209	$77.22	$77.20	$77.20
7 purchase totals =	$910.96		$1,002.5835	$1,002.58	$1,002.50	$1,002.60