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	$73.59	7.537%	$79.1365	$79.14	$79.15	$79.10
Purchase #2	$145.46	13.859%	$165.6193	$165.62	$165.60	$165.60
Purchase #3	$179.33	7.393%	$192.5879	$192.59	$192.60	$192.60
Purchase #4	$127.45	10.194%	$140.4423	$140.44	$140.45	$140.40
Purchase #5	$105.39	10.344%	$116.2915	$116.29	$116.30	$116.30
Purchase #6	$97.82	5.416%	$103.1179	$103.12	$103.10	$103.10
Purchase #7	$122.43	5.275%	$128.8882	$128.89	$128.90	$128.90
7 purchase totals =	$851.47		$926.0836	$926.09	$926.10	$926.00