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	$111.67	4.588%	$116.7934	$116.79	$116.80	$116.80
Purchase #2	$229.86	10.323%	$253.5884	$253.59	$253.60	$253.60
Purchase #3	$63.39	11.628%	$70.761	$70.76	$70.75	$70.80
Purchase #4	$145.52	13.787%	$165.5828	$165.58	$165.60	$165.60
Purchase #5	$87.60	3.212%	$90.4137	$90.41	$90.40	$90.40
Purchase #6	$203.80	9.654%	$223.4749	$223.47	$223.45	$223.50
Purchase #7	$173.30	10.664%	$191.7807	$191.78	$191.80	$191.80
7 purchase totals =	$1,015.14		$1,112.3949	$1,112.38	$1,112.40	$1,112.50