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	$208.98	6.314%	$222.175	$222.18	$222.20	$222.20
Purchase #2	$153.42	4.344%	$160.0846	$160.08	$160.10	$160.10
Purchase #3	$118.90	5.376%	$125.2921	$125.29	$125.30	$125.30
Purchase #4	$162.68	5.802%	$172.1187	$172.12	$172.10	$172.10
Purchase #5	$85.28	8.270%	$92.3327	$92.33	$92.35	$92.30
Purchase #6	$96.77	13.167%	$109.5117	$109.51	$109.50	$109.50
Purchase #7	$53.82	8.848%	$58.582	$58.58	$58.60	$58.60
7 purchase totals =	$879.85		$940.0968	$940.09	$940.15	$940.10