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	$139.72	10.523%	$154.4227	$154.42	$154.40	$154.40
Purchase #2	$34.83	13.810%	$39.64	$39.64	$39.65	$39.60
Purchase #3	$88.64	4.680%	$92.7884	$92.79	$92.80	$92.80
Purchase #4	$74.48	9.423%	$81.4983	$81.50	$81.50	$81.50
Purchase #5	$45.79	4.283%	$47.7512	$47.75	$47.75	$47.80
Purchase #6	$101.38	10.242%	$111.7633	$111.76	$111.75	$111.80
Purchase #7	$60.89	10.702%	$67.4064	$67.41	$67.40	$67.40
7 purchase totals =	$545.73		$595.2703	$595.27	$595.25	$595.30