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	$113.51	12.211%	$127.3707	$127.37	$127.35	$127.40
Purchase #2	$66.62	10.445%	$73.5785	$73.58	$73.60	$73.60
Purchase #3	$37.86	13.681%	$43.0396	$43.04	$43.05	$43.00
Purchase #4	$127.37	11.583%	$142.1233	$142.12	$142.10	$142.10
Purchase #5	$91.43	11.603%	$102.0386	$102.04	$102.05	$102.00
Purchase #6	$245.52	10.474%	$271.2358	$271.24	$271.25	$271.20
Purchase #7	$118.43	3.185%	$122.202	$122.20	$122.20	$122.20
7 purchase totals =	$800.74		$881.5885	$881.59	$881.60	$881.50