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	$81.79	4.695%	$85.63	$85.63	$85.65	$85.60
Purchase #2	$43.75	6.264%	$46.4905	$46.49	$46.50	$46.50
Purchase #3	$133.88	12.519%	$150.6404	$150.64	$150.65	$150.60
Purchase #4	$155.53	8.259%	$168.3752	$168.38	$168.40	$168.40
Purchase #5	$82.86	6.501%	$88.2467	$88.25	$88.25	$88.20
Purchase #6	$54.33	4.528%	$56.7901	$56.79	$56.80	$56.80
Purchase #7	$13.28	10.124%	$14.6245	$14.62	$14.60	$14.60
7 purchase totals =	$565.42		$610.7974	$610.80	$610.85	$610.70