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	$94.94	7.307%	$101.8773	$101.88	$101.90	$101.90
Purchase #2	$28.45	13.412%	$32.2657	$32.27	$32.25	$32.30
Purchase #3	$47.54	6.300%	$50.535	$50.54	$50.55	$50.50
Purchase #4	$54.74	3.397%	$56.5995	$56.60	$56.60	$56.60
Purchase #5	$48.52	5.584%	$51.2294	$51.23	$51.25	$51.20
Purchase #6	$156.91	10.819%	$173.8861	$173.89	$173.90	$173.90
Purchase #7	$16.80	9.397%	$18.3787	$18.38	$18.40	$18.40
7 purchase totals =	$447.90		$484.7717	$484.79	$484.85	$484.80