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	$180.64	10.798%	$200.1455	$200.15	$200.15	$200.10
Purchase #2	$38.37	5.689%	$40.5529	$40.55	$40.55	$40.60
Purchase #3	$211.42	13.393%	$239.7355	$239.74	$239.75	$239.70
Purchase #4	$81.82	10.732%	$90.6009	$90.60	$90.60	$90.60
Purchase #5	$41.26	10.346%	$45.5288	$45.53	$45.55	$45.50
Purchase #6	$242.61	12.172%	$272.1405	$272.14	$272.15	$272.10
Purchase #7	$76.25	7.507%	$81.9741	$81.97	$81.95	$82.00
7 purchase totals =	$872.37		$970.6782	$970.68	$970.70	$970.60