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	$103.77	6.372%	$110.3822	$110.38	$110.40	$110.40
Purchase #2	$12.32	12.542%	$13.8652	$13.87	$13.85	$13.90
Purchase #3	$43.56	4.301%	$45.4335	$45.43	$45.45	$45.40
Purchase #4	$175.51	5.822%	$185.7282	$185.73	$185.75	$185.70
Purchase #5	$173.25	8.210%	$187.4738	$187.47	$187.45	$187.50
Purchase #6	$169.53	11.636%	$189.2565	$189.26	$189.25	$189.30
Purchase #7	$26.76	11.141%	$29.7413	$29.74	$29.75	$29.70
7 purchase totals =	$704.70		$761.8807	$761.88	$761.90	$761.90