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	$162.40	5.830%	$171.8679	$171.87	$171.85	$171.90
Purchase #2	$53.27	6.342%	$56.6484	$56.65	$56.65	$56.60
Purchase #3	$161.86	12.321%	$181.8028	$181.80	$181.80	$181.80
Purchase #4	$156.95	11.441%	$174.9066	$174.91	$174.90	$174.90
Purchase #5	$31.49	3.419%	$32.5666	$32.57	$32.55	$32.60
Purchase #6	$74.94	10.444%	$82.7667	$82.77	$82.75	$82.80
Purchase #7	$25.75	13.628%	$29.2592	$29.26	$29.25	$29.30
7 purchase totals =	$666.66		$729.8182	$729.83	$729.75	$729.90