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	$120.82	5.132%	$127.0205	$127.02	$127.00	$127.00
Purchase #2	$75.31	8.855%	$81.9787	$81.98	$82.00	$82.00
Purchase #3	$137.35	9.309%	$150.1359	$150.14	$150.15	$150.10
Purchase #4	$41.25	5.679%	$43.5926	$43.59	$43.60	$43.60
Purchase #5	$79.73	11.806%	$89.1429	$89.14	$89.15	$89.10
Purchase #6	$130.25	6.214%	$138.3437	$138.34	$138.35	$138.30
Purchase #7	$217.96	11.551%	$243.1366	$243.14	$243.15	$243.10
7 purchase totals =	$802.67		$873.3509	$873.35	$873.40	$873.20