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	$198.53	9.865%	$218.115	$218.12	$218.10	$218.10
Purchase #2	$237.40	5.671%	$250.863	$250.86	$250.85	$250.90
Purchase #3	$165.90	8.239%	$179.5685	$179.57	$179.55	$179.60
Purchase #4	$60.72	8.667%	$65.9826	$65.98	$66.00	$66.00
Purchase #5	$225.31	13.414%	$255.5331	$255.53	$255.55	$255.50
Purchase #6	$166.27	3.730%	$172.4719	$172.47	$172.45	$172.50
Purchase #7	$207.98	5.113%	$218.614	$218.61	$218.60	$218.60
7 purchase totals =	$1,262.11		$1,361.1481	$1,361.14	$1,361.10	$1,361.20