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	$140.77	11.378%	$156.7868	$156.79	$156.80	$156.80
Purchase #2	$28.27	12.826%	$31.8959	$31.90	$31.90	$31.90
Purchase #3	$172.49	12.859%	$194.6705	$194.67	$194.65	$194.70
Purchase #4	$121.64	4.448%	$127.0505	$127.05	$127.05	$127.10
Purchase #5	$200.59	9.616%	$219.8787	$219.88	$219.90	$219.90
Purchase #6	$230.86	5.370%	$243.2572	$243.26	$243.25	$243.30
Purchase #7	$32.85	5.393%	$34.6216	$34.62	$34.60	$34.60
7 purchase totals =	$927.47		$1,008.1612	$1,008.17	$1,008.15	$1,008.30