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	$112.79	13.429%	$127.9366	$127.94	$127.95	$127.90
Purchase #2	$98.88	12.334%	$111.0759	$111.08	$111.10	$111.10
Purchase #3	$112.99	9.135%	$123.3116	$123.31	$123.30	$123.30
Purchase #4	$104.77	4.279%	$109.2531	$109.25	$109.25	$109.30
Purchase #5	$179.41	7.644%	$193.1241	$193.12	$193.10	$193.10
Purchase #6	$19.80	8.254%	$21.4343	$21.43	$21.45	$21.40
Purchase #7	$219.86	6.598%	$234.3664	$234.37	$234.35	$234.40
7 purchase totals =	$848.50		$920.5020	$920.50	$920.50	$920.50