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	$127.66	9.156%	$139.3485	$139.35	$139.35	$139.30
Purchase #2	$136.39	12.104%	$152.8986	$152.90	$152.90	$152.90
Purchase #3	$44.62	8.216%	$48.286	$48.29	$48.30	$48.30
Purchase #4	$26.43	4.783%	$27.6941	$27.69	$27.70	$27.70
Purchase #5	$82.52	10.602%	$91.2688	$91.27	$91.25	$91.30
Purchase #6	$82.96	5.116%	$87.2042	$87.20	$87.20	$87.20
Purchase #7	$154.80	7.330%	$166.1468	$166.15	$166.15	$166.10
7 purchase totals =	$655.38		$712.8470	$712.85	$712.85	$712.80