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	$94.85	10.457%	$104.7685	$104.77	$104.75	$104.80
Purchase #2	$155.28	13.648%	$176.4726	$176.47	$176.45	$176.50
Purchase #3	$149.87	9.455%	$164.0402	$164.04	$164.05	$164.00
Purchase #4	$158.58	13.134%	$179.4079	$179.41	$179.40	$179.40
Purchase #5	$118.34	4.534%	$123.7055	$123.71	$123.70	$123.70
Purchase #6	$146.80	3.740%	$152.2903	$152.29	$152.30	$152.30
Purchase #7	$103.70	7.421%	$111.3956	$111.40	$111.40	$111.40
7 purchase totals =	$927.42		$1,012.0806	$1,012.09	$1,012.05	$1,012.10