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	$222.49	9.392%	$243.3863	$243.39	$243.40	$243.40
Purchase #2	$53.32	11.811%	$59.6176	$59.62	$59.60	$59.60
Purchase #3	$216.69	5.431%	$228.4584	$228.46	$228.45	$228.50
Purchase #4	$43.77	4.141%	$45.5825	$45.58	$45.60	$45.60
Purchase #5	$29.79	12.866%	$33.6228	$33.62	$33.60	$33.60
Purchase #6	$188.92	8.609%	$205.1841	$205.18	$205.20	$205.20
Purchase #7	$219.85	13.862%	$250.3256	$250.33	$250.35	$250.30
7 purchase totals =	$974.83		$1,066.1773	$1,066.18	$1,066.20	$1,066.20