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	$186.64	5.466%	$196.8417	$196.84	$196.85	$196.80
Purchase #2	$238.36	11.824%	$266.5437	$266.54	$266.55	$266.50
Purchase #3	$152.87	7.390%	$164.1671	$164.17	$164.15	$164.20
Purchase #4	$55.65	6.391%	$59.2066	$59.21	$59.20	$59.20
Purchase #5	$112.43	6.258%	$119.4659	$119.47	$119.45	$119.50
Purchase #6	$20.35	10.657%	$22.5187	$22.52	$22.50	$22.50
Purchase #7	$128.27	9.302%	$140.2017	$140.20	$140.20	$140.20
7 purchase totals =	$894.57		$968.9454	$968.95	$968.90	$968.90