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	$152.57	7.680%	$164.2874	$164.29	$164.30	$164.30
Purchase #2	$192.56	11.649%	$214.9913	$214.99	$215.00	$215.00
Purchase #3	$191.36	7.261%	$205.2546	$205.25	$205.25	$205.30
Purchase #4	$135.49	11.622%	$151.2366	$151.24	$151.25	$151.20
Purchase #5	$103.49	5.461%	$109.1416	$109.14	$109.15	$109.10
Purchase #6	$51.74	5.611%	$54.6431	$54.64	$54.65	$54.60
Purchase #7	$180.92	13.550%	$205.4347	$205.43	$205.45	$205.40
7 purchase totals =	$1,008.13		$1,104.9893	$1,104.98	$1,105.05	$1,104.90