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	$186.59	12.224%	$209.3988	$209.40	$209.40	$209.40
Purchase #2	$115.95	3.363%	$119.8494	$119.85	$119.85	$119.80
Purchase #3	$220.67	5.817%	$233.5064	$233.51	$233.50	$233.50
Purchase #4	$214.87	6.850%	$229.5886	$229.59	$229.60	$229.60
Purchase #5	$100.25	9.451%	$109.7246	$109.72	$109.70	$109.70
Purchase #6	$162.90	7.832%	$175.6583	$175.66	$175.65	$175.70
Purchase #7	$116.37	9.409%	$127.3193	$127.32	$127.30	$127.30
7 purchase totals =	$1,117.60		$1,205.0454	$1,205.05	$1,205.00	$1,205.00