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	$153.54	4.686%	$160.7349	$160.73	$160.75	$160.70
Purchase #2	$48.70	5.496%	$51.3766	$51.38	$51.40	$51.40
Purchase #3	$45.47	9.815%	$49.9329	$49.93	$49.95	$49.90
Purchase #4	$54.26	9.868%	$59.6144	$59.61	$59.60	$59.60
Purchase #5	$25.86	8.730%	$28.1176	$28.12	$28.10	$28.10
Purchase #6	$147.98	3.650%	$153.3813	$153.38	$153.40	$153.40
Purchase #7	$173.34	5.123%	$182.2202	$182.22	$182.20	$182.20
7 purchase totals =	$649.15		$685.3779	$685.37	$685.40	$685.30