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	$103.79	7.176%	$111.238	$111.24	$111.25	$111.20
Purchase #2	$96.69	7.527%	$103.9679	$103.97	$103.95	$104.00
Purchase #3	$83.42	10.484%	$92.1658	$92.17	$92.15	$92.20
Purchase #4	$6.40	10.405%	$7.0659	$7.07	$7.05	$7.10
Purchase #5	$113.90	3.669%	$118.079	$118.08	$118.10	$118.10
Purchase #6	$167.55	4.347%	$174.8334	$174.83	$174.85	$174.80
Purchase #7	$220.71	10.604%	$244.1141	$244.11	$244.10	$244.10
7 purchase totals =	$792.46		$851.4641	$851.47	$851.45	$851.50