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	$159.96	3.810%	$166.0545	$166.05	$166.05	$166.10
Purchase #2	$213.75	12.684%	$240.8621	$240.86	$240.85	$240.90
Purchase #3	$168.46	4.753%	$176.4669	$176.47	$176.45	$176.50
Purchase #4	$149.27	10.208%	$164.5075	$164.51	$164.50	$164.50
Purchase #5	$48.92	13.671%	$55.6079	$55.61	$55.60	$55.60
Purchase #6	$37.66	3.567%	$39.0033	$39.00	$39.00	$39.00
Purchase #7	$165.71	4.131%	$172.5555	$172.56	$172.55	$172.60
7 purchase totals =	$943.73		$1,015.0577	$1,015.06	$1,015.00	$1,015.20