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	$43.95	3.766%	$45.6052	$45.61	$45.60	$45.60
Purchase #2	$116.37	8.462%	$126.2172	$126.22	$126.20	$126.20
Purchase #3	$201.43	5.449%	$212.4059	$212.41	$212.40	$212.40
Purchase #4	$184.43	5.136%	$193.9023	$193.90	$193.90	$193.90
Purchase #5	$92.80	13.812%	$105.6175	$105.62	$105.60	$105.60
Purchase #6	$244.73	9.443%	$267.8399	$267.84	$267.85	$267.80
Purchase #7	$113.60	12.287%	$127.558	$127.56	$127.55	$127.60
7 purchase totals =	$997.31		$1,079.1460	$1,079.16	$1,079.10	$1,079.10