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	$83.85	13.751%	$95.3802	$95.38	$95.40	$95.40
Purchase #2	$239.34	3.814%	$248.4684	$248.47	$248.45	$248.50
Purchase #3	$140.56	4.383%	$146.7207	$146.72	$146.70	$146.70
Purchase #4	$81.52	8.522%	$88.4671	$88.47	$88.45	$88.50
Purchase #5	$167.95	6.147%	$178.2739	$178.27	$178.25	$178.30
Purchase #6	$127.94	8.280%	$138.5334	$138.53	$138.55	$138.50
Purchase #7	$144.68	12.388%	$162.603	$162.60	$162.60	$162.60
7 purchase totals =	$985.84		$1,058.4467	$1,058.44	$1,058.40	$1,058.50