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	$167.73	7.232%	$179.8602	$179.86	$179.85	$179.90
Purchase #2	$30.91	5.411%	$32.5825	$32.58	$32.60	$32.60
Purchase #3	$161.88	12.346%	$181.8657	$181.87	$181.85	$181.90
Purchase #4	$164.27	12.745%	$185.2062	$185.21	$185.20	$185.20
Purchase #5	$184.47	10.163%	$203.2177	$203.22	$203.20	$203.20
Purchase #6	$237.52	7.612%	$255.6	$255.60	$255.60	$255.60
Purchase #7	$154.38	10.846%	$171.1241	$171.12	$171.10	$171.10
7 purchase totals =	$1,101.16		$1,209.4564	$1,209.46	$1,209.40	$1,209.50