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	$231.49	6.174%	$245.7822	$245.78	$245.80	$245.80
Purchase #2	$91.73	13.118%	$103.7631	$103.76	$103.75	$103.80
Purchase #3	$147.27	13.483%	$167.1264	$167.13	$167.15	$167.10
Purchase #4	$78.87	4.350%	$82.3008	$82.30	$82.30	$82.30
Purchase #5	$229.85	11.136%	$255.4461	$255.45	$255.45	$255.40
Purchase #6	$125.43	11.612%	$139.9949	$139.99	$140.00	$140.00
Purchase #7	$10.60	13.408%	$12.0212	$12.02	$12.00	$12.00
7 purchase totals =	$915.24		$1,006.4347	$1,006.43	$1,006.45	$1,006.40