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	$229.58	8.577%	$249.2711	$249.27	$249.25	$249.30
Purchase #2	$19.48	3.734%	$20.2074	$20.21	$20.20	$20.20
Purchase #3	$120.43	4.299%	$125.6073	$125.61	$125.60	$125.60
Purchase #4	$41.96	4.296%	$43.7626	$43.76	$43.75	$43.80
Purchase #5	$64.25	11.309%	$71.516	$71.52	$71.50	$71.50
Purchase #6	$38.99	13.553%	$44.2743	$44.27	$44.25	$44.30
Purchase #7	$205.77	13.689%	$233.9379	$233.94	$233.95	$233.90
7 purchase totals =	$720.46		$788.5766	$788.58	$788.50	$788.60