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	$243.97	3.354%	$252.1528	$252.15	$252.15	$252.20
Purchase #2	$80.46	3.470%	$83.252	$83.25	$83.25	$83.30
Purchase #3	$222.35	10.377%	$245.4233	$245.42	$245.40	$245.40
Purchase #4	$130.47	8.347%	$141.3603	$141.36	$141.35	$141.40
Purchase #5	$204.83	5.183%	$215.4463	$215.45	$215.45	$215.40
Purchase #6	$111.36	13.666%	$126.5785	$126.58	$126.60	$126.60
Purchase #7	$32.62	11.188%	$36.2695	$36.27	$36.25	$36.30
7 purchase totals =	$1,026.06		$1,100.4827	$1,100.48	$1,100.45	$1,100.60