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	$133.64	5.226%	$140.624	$140.62	$140.60	$140.60
Purchase #2	$157.55	13.549%	$178.8964	$178.90	$178.90	$178.90
Purchase #3	$186.64	5.141%	$196.2352	$196.24	$196.25	$196.20
Purchase #4	$158.27	12.702%	$178.3735	$178.37	$178.35	$178.40
Purchase #5	$235.27	13.606%	$267.2808	$267.28	$267.30	$267.30
Purchase #6	$49.83	3.362%	$51.5053	$51.51	$51.50	$51.50
Purchase #7	$235.71	11.303%	$262.3523	$262.35	$262.35	$262.40
7 purchase totals =	$1,156.91		$1,275.2675	$1,275.27	$1,275.25	$1,275.30