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	$151.81	8.601%	$164.8672	$164.87	$164.85	$164.90
Purchase #2	$179.40	7.260%	$192.4244	$192.42	$192.40	$192.40
Purchase #3	$179.83	10.200%	$198.1727	$198.17	$198.15	$198.20
Purchase #4	$236.66	13.574%	$268.7842	$268.78	$268.80	$268.80
Purchase #5	$249.59	4.623%	$261.1285	$261.13	$261.15	$261.10
Purchase #6	$79.54	8.805%	$86.5435	$86.54	$86.55	$86.50
Purchase #7	$76.26	9.408%	$83.4345	$83.43	$83.45	$83.40
7 purchase totals =	$1,153.09		$1,255.3550	$1,255.34	$1,255.35	$1,255.30