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	$98.40	3.588%	$101.9306	$101.93	$101.95	$101.90
Purchase #2	$219.66	3.866%	$228.1521	$228.15	$228.15	$228.20
Purchase #3	$68.93	3.874%	$71.6003	$71.60	$71.60	$71.60
Purchase #4	$97.44	12.693%	$109.8081	$109.81	$109.80	$109.80
Purchase #5	$102.62	5.485%	$108.2487	$108.25	$108.25	$108.20
Purchase #6	$106.89	8.853%	$116.353	$116.35	$116.35	$116.40
Purchase #7	$95.80	3.680%	$99.3254	$99.33	$99.35	$99.30
7 purchase totals =	$789.74		$835.4182	$835.42	$835.45	$835.40