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	$119.59	8.214%	$129.4131	$129.41	$129.40	$129.40
Purchase #2	$38.89	11.423%	$43.3324	$43.33	$43.35	$43.30
Purchase #3	$103.44	7.848%	$111.558	$111.56	$111.55	$111.60
Purchase #4	$58.84	9.637%	$64.5104	$64.51	$64.50	$64.50
Purchase #5	$38.96	5.403%	$41.065	$41.07	$41.05	$41.10
Purchase #6	$45.93	5.388%	$48.4047	$48.40	$48.40	$48.40
Purchase #7	$113.73	4.466%	$118.8092	$118.81	$118.80	$118.80
7 purchase totals =	$519.38		$557.0928	$557.09	$557.05	$557.10