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	$138.92	5.323%	$146.3147	$146.31	$146.30	$146.30
Purchase #2	$69.28	6.561%	$73.8255	$73.83	$73.85	$73.80
Purchase #3	$118.25	7.430%	$127.036	$127.04	$127.05	$127.00
Purchase #4	$39.70	6.170%	$42.1495	$42.15	$42.15	$42.10
Purchase #5	$216.76	5.336%	$228.3263	$228.33	$228.35	$228.30
Purchase #6	$249.34	9.222%	$272.3341	$272.33	$272.35	$272.30
Purchase #7	$23.89	3.833%	$24.8057	$24.81	$24.80	$24.80
7 purchase totals =	$856.14		$914.7918	$914.80	$914.85	$914.60