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	$87.51	3.316%	$90.4118	$90.41	$90.40	$90.40
Purchase #2	$46.96	7.755%	$50.6017	$50.60	$50.60	$50.60
Purchase #3	$6.49	8.368%	$7.0331	$7.03	$7.05	$7.00
Purchase #4	$59.93	10.407%	$66.1669	$66.17	$66.15	$66.20
Purchase #5	$95.62	4.108%	$99.5481	$99.55	$99.55	$99.50
Purchase #6	$156.97	12.155%	$176.0497	$176.05	$176.05	$176.00
Purchase #7	$210.78	5.602%	$222.5879	$222.59	$222.60	$222.60
7 purchase totals =	$664.26		$712.3992	$712.40	$712.40	$712.30