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	$119.94	11.372%	$133.5796	$133.58	$133.60	$133.60
Purchase #2	$12.67	7.401%	$13.6077	$13.61	$13.60	$13.60
Purchase #3	$233.25	6.814%	$249.1437	$249.14	$249.15	$249.10
Purchase #4	$64.27	4.219%	$66.9816	$66.98	$67.00	$67.00
Purchase #5	$107.60	11.174%	$119.6232	$119.62	$119.60	$119.60
Purchase #6	$82.73	8.134%	$89.4593	$89.46	$89.45	$89.50
Purchase #7	$88.51	8.614%	$96.1343	$96.13	$96.15	$96.10
7 purchase totals =	$708.97		$768.5294	$768.52	$768.55	$768.50