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	$54.62	8.812%	$59.4331	$59.43	$59.45	$59.40
Purchase #2	$34.52	12.405%	$38.8022	$38.80	$38.80	$38.80
Purchase #3	$55.43	7.326%	$59.4908	$59.49	$59.50	$59.50
Purchase #4	$11.40	6.164%	$12.1027	$12.10	$12.10	$12.10
Purchase #5	$9.45	11.375%	$10.5249	$10.52	$10.50	$10.50
Purchase #6	$96.88	4.471%	$101.2115	$101.21	$101.20	$101.20
Purchase #7	$201.63	6.106%	$213.9415	$213.94	$213.95	$213.90
7 purchase totals =	$463.93		$495.5067	$495.49	$495.50	$495.40