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	$14.76	8.277%	$15.9817	$15.98	$16.00	$16.00
Purchase #2	$80.84	6.673%	$86.2345	$86.23	$86.25	$86.20
Purchase #3	$44.87	7.208%	$48.1042	$48.10	$48.10	$48.10
Purchase #4	$167.86	7.405%	$180.29	$180.29	$180.30	$180.30
Purchase #5	$69.84	3.329%	$72.165	$72.17	$72.15	$72.20
Purchase #6	$78.34	5.849%	$82.9221	$82.92	$82.90	$82.90
Purchase #7	$145.57	13.480%	$165.1928	$165.19	$165.20	$165.20
7 purchase totals =	$602.08		$650.8903	$650.88	$650.90	$650.90