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	$155.54	5.666%	$164.3529	$164.35	$164.35	$164.40
Purchase #2	$166.88	10.147%	$183.8133	$183.81	$183.80	$183.80
Purchase #3	$42.25	8.601%	$45.8839	$45.88	$45.90	$45.90
Purchase #4	$18.72	12.356%	$21.033	$21.03	$21.05	$21.00
Purchase #5	$168.49	3.741%	$174.7932	$174.79	$174.80	$174.80
Purchase #6	$142.75	5.705%	$150.8939	$150.89	$150.90	$150.90
Purchase #7	$177.56	4.403%	$185.378	$185.38	$185.40	$185.40
7 purchase totals =	$872.19		$926.1482	$926.13	$926.20	$926.20