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	$98.95	12.236%	$111.0575	$111.06	$111.05	$111.10
Purchase #2	$139.46	4.228%	$145.3564	$145.36	$145.35	$145.40
Purchase #3	$179.49	13.735%	$204.143	$204.14	$204.15	$204.10
Purchase #4	$205.36	9.144%	$224.1381	$224.14	$224.15	$224.10
Purchase #5	$91.88	13.762%	$104.5245	$104.52	$104.50	$104.50
Purchase #6	$240.59	13.138%	$272.1987	$272.20	$272.20	$272.20
Purchase #7	$218.94	6.688%	$233.5827	$233.58	$233.60	$233.60
7 purchase totals =	$1,174.67		$1,295.0009	$1,295.00	$1,295.00	$1,295.00