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	$128.27	13.383%	$145.4364	$145.44	$145.45	$145.40
Purchase #2	$127.85	10.739%	$141.5798	$141.58	$141.60	$141.60
Purchase #3	$240.27	5.141%	$252.6223	$252.62	$252.60	$252.60
Purchase #4	$141.79	13.435%	$160.8395	$160.84	$160.85	$160.80
Purchase #5	$162.31	12.573%	$182.7172	$182.72	$182.70	$182.70
Purchase #6	$73.31	13.639%	$83.3088	$83.31	$83.30	$83.30
Purchase #7	$138.33	5.420%	$145.8275	$145.83	$145.85	$145.80
7 purchase totals =	$1,012.13		$1,112.3315	$1,112.34	$1,112.35	$1,112.20