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	$134.26	10.486%	$148.3385	$148.34	$148.35	$148.30
Purchase #2	$157.85	9.260%	$172.4669	$172.47	$172.45	$172.50
Purchase #3	$53.41	10.685%	$59.1169	$59.12	$59.10	$59.10
Purchase #4	$119.56	10.648%	$132.2907	$132.29	$132.30	$132.30
Purchase #5	$99.93	4.397%	$104.3239	$104.32	$104.30	$104.30
Purchase #6	$46.86	8.343%	$50.7695	$50.77	$50.75	$50.80
Purchase #7	$246.31	6.675%	$262.7512	$262.75	$262.75	$262.80
7 purchase totals =	$858.18		$930.0576	$930.06	$930.00	$930.10