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	$225.94	10.640%	$249.98	$249.98	$250.00	$250.00
Purchase #2	$101.70	9.160%	$111.0157	$111.02	$111.00	$111.00
Purchase #3	$122.33	3.535%	$126.6544	$126.65	$126.65	$126.70
Purchase #4	$146.81	3.162%	$151.4521	$151.45	$151.45	$151.50
Purchase #5	$140.43	9.528%	$153.8102	$153.81	$153.80	$153.80
Purchase #6	$181.50	4.681%	$189.996	$190.00	$190.00	$190.00
Purchase #7	$41.82	8.337%	$45.3065	$45.31	$45.30	$45.30
7 purchase totals =	$960.53		$1,028.2149	$1,028.22	$1,028.20	$1,028.30