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	$202.40	5.441%	$213.4126	$213.41	$213.40	$213.40
Purchase #2	$100.82	10.333%	$111.2377	$111.24	$111.25	$111.20
Purchase #3	$94.55	7.696%	$101.8266	$101.83	$101.85	$101.80
Purchase #4	$103.60	13.102%	$117.1737	$117.17	$117.15	$117.20
Purchase #5	$185.65	9.622%	$203.5132	$203.51	$203.50	$203.50
Purchase #6	$37.49	8.403%	$40.6403	$40.64	$40.65	$40.60
Purchase #7	$94.79	4.792%	$99.3323	$99.33	$99.35	$99.30
7 purchase totals =	$819.30		$887.1364	$887.13	$887.15	$887.00