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	$216.79	11.425%	$241.5583	$241.56	$241.55	$241.60
Purchase #2	$117.52	8.776%	$127.8336	$127.83	$127.85	$127.80
Purchase #3	$181.35	7.714%	$195.3393	$195.34	$195.35	$195.30
Purchase #4	$5.63	4.321%	$5.8733	$5.87	$5.85	$5.90
Purchase #5	$151.67	9.378%	$165.8936	$165.89	$165.90	$165.90
Purchase #6	$224.56	4.583%	$234.8516	$234.85	$234.85	$234.90
Purchase #7	$42.26	3.830%	$43.8786	$43.88	$43.90	$43.90
7 purchase totals =	$939.78		$1,015.2283	$1,015.22	$1,015.25	$1,015.30