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	$196.74	8.491%	$213.4452	$213.45	$213.45	$213.40
Purchase #2	$13.41	7.170%	$14.3715	$14.37	$14.35	$14.40
Purchase #3	$246.92	10.447%	$272.7157	$272.72	$272.70	$272.70
Purchase #4	$130.37	11.524%	$145.3938	$145.39	$145.40	$145.40
Purchase #5	$155.36	11.292%	$172.9033	$172.90	$172.90	$172.90
Purchase #6	$234.62	8.392%	$254.3093	$254.31	$254.30	$254.30
Purchase #7	$93.33	6.161%	$99.0801	$99.08	$99.10	$99.10
7 purchase totals =	$1,070.75		$1,172.2189	$1,172.22	$1,172.20	$1,172.20