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	$246.88	8.188%	$267.0945	$267.09	$267.10	$267.10
Purchase #2	$156.34	10.701%	$173.0699	$173.07	$173.05	$173.10
Purchase #3	$61.61	6.454%	$65.5863	$65.59	$65.60	$65.60
Purchase #4	$87.83	6.856%	$93.8516	$93.85	$93.85	$93.90
Purchase #5	$234.52	11.345%	$261.1263	$261.13	$261.15	$261.10
Purchase #6	$154.79	7.346%	$166.1609	$166.16	$166.15	$166.20
Purchase #7	$150.57	12.436%	$169.2949	$169.29	$169.30	$169.30
7 purchase totals =	$1,092.54		$1,196.1844	$1,196.18	$1,196.20	$1,196.30