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	$194.32	12.809%	$219.2104	$219.21	$219.20	$219.20
Purchase #2	$241.29	6.463%	$256.8846	$256.88	$256.90	$256.90
Purchase #3	$213.82	9.187%	$233.4636	$233.46	$233.45	$233.50
Purchase #4	$114.29	11.648%	$127.6025	$127.60	$127.60	$127.60
Purchase #5	$112.65	13.461%	$127.8138	$127.81	$127.80	$127.80
Purchase #6	$101.40	10.573%	$112.121	$112.12	$112.10	$112.10
Purchase #7	$57.92	9.418%	$63.3749	$63.37	$63.35	$63.40
7 purchase totals =	$1,035.69		$1,140.4708	$1,140.45	$1,140.40	$1,140.50