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	$55.70	13.111%	$63.0028	$63.00	$63.00	$63.00
Purchase #2	$39.56	9.742%	$43.4139	$43.41	$43.40	$43.40
Purchase #3	$231.94	10.144%	$255.468	$255.47	$255.45	$255.50
Purchase #4	$219.87	13.555%	$249.6734	$249.67	$249.65	$249.70
Purchase #5	$158.88	4.136%	$165.4513	$165.45	$165.45	$165.50
Purchase #6	$153.48	3.461%	$158.7919	$158.79	$158.80	$158.80
Purchase #7	$233.75	4.857%	$245.1032	$245.10	$245.10	$245.10
7 purchase totals =	$1,093.18		$1,180.9045	$1,180.89	$1,180.85	$1,181.00