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	$173.33	12.212%	$194.4971	$194.50	$194.50	$194.50
Purchase #2	$104.53	7.165%	$112.0196	$112.02	$112.00	$112.00
Purchase #3	$101.56	4.673%	$106.3059	$106.31	$106.30	$106.30
Purchase #4	$64.42	6.343%	$68.5062	$68.51	$68.50	$68.50
Purchase #5	$241.62	7.388%	$259.4709	$259.47	$259.45	$259.50
Purchase #6	$100.45	4.869%	$105.3409	$105.34	$105.35	$105.30
Purchase #7	$117.59	4.727%	$123.1485	$123.15	$123.15	$123.10
7 purchase totals =	$903.50		$969.2891	$969.30	$969.25	$969.20