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	$185.58	10.500%	$205.0659	$205.07	$205.05	$205.10
Purchase #2	$250.50	6.704%	$267.2935	$267.29	$267.30	$267.30
Purchase #3	$227.65	11.383%	$253.5634	$253.56	$253.55	$253.60
Purchase #4	$169.83	11.206%	$188.8611	$188.86	$188.85	$188.90
Purchase #5	$48.90	11.522%	$54.5343	$54.53	$54.55	$54.50
Purchase #6	$25.68	10.767%	$28.445	$28.45	$28.45	$28.40
Purchase #7	$241.32	3.395%	$249.5128	$249.51	$249.50	$249.50
7 purchase totals =	$1,149.46		$1,247.2760	$1,247.27	$1,247.25	$1,247.30