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	$150.57	7.675%	$162.1262	$162.13	$162.15	$162.10
Purchase #2	$190.38	13.250%	$215.6054	$215.61	$215.60	$215.60
Purchase #3	$133.28	11.597%	$148.7365	$148.74	$148.75	$148.70
Purchase #4	$181.66	10.401%	$200.5545	$200.55	$200.55	$200.60
Purchase #5	$49.43	10.868%	$54.8021	$54.80	$54.80	$54.80
Purchase #6	$185.95	12.269%	$208.7642	$208.76	$208.75	$208.80
Purchase #7	$220.73	4.484%	$230.6275	$230.63	$230.65	$230.60
7 purchase totals =	$1,112.00		$1,221.2164	$1,221.22	$1,221.25	$1,221.20