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	$47.77	9.193%	$52.1615	$52.16	$52.15	$52.20
Purchase #2	$78.37	11.779%	$87.6012	$87.60	$87.60	$87.60
Purchase #3	$99.71	6.665%	$106.3557	$106.36	$106.35	$106.40
Purchase #4	$237.60	13.593%	$269.897	$269.90	$269.90	$269.90
Purchase #5	$56.37	13.450%	$63.9518	$63.95	$63.95	$64.00
Purchase #6	$173.59	3.297%	$179.3133	$179.31	$179.30	$179.30
Purchase #7	$237.92	4.713%	$249.1332	$249.13	$249.15	$249.10
7 purchase totals =	$931.33		$1,008.4137	$1,008.41	$1,008.40	$1,008.50