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	$103.95	9.754%	$114.0893	$114.09	$114.10	$114.10
Purchase #2	$38.55	3.612%	$39.9424	$39.94	$39.95	$39.90
Purchase #3	$47.73	12.271%	$53.5869	$53.59	$53.60	$53.60
Purchase #4	$112.53	3.276%	$116.2165	$116.22	$116.20	$116.20
Purchase #5	$158.98	3.834%	$165.0753	$165.08	$165.10	$165.10
Purchase #6	$81.52	12.735%	$91.9016	$91.90	$91.90	$91.90
Purchase #7	$172.46	3.409%	$178.3392	$178.34	$178.35	$178.30
7 purchase totals =	$715.72		$759.1512	$759.16	$759.20	$759.10