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	$185.73	7.733%	$200.0925	$200.09	$200.10	$200.10
Purchase #2	$217.60	7.217%	$233.3042	$233.30	$233.30	$233.30
Purchase #3	$63.67	13.456%	$72.2374	$72.24	$72.25	$72.20
Purchase #4	$96.34	4.178%	$100.3651	$100.37	$100.35	$100.40
Purchase #5	$179.35	10.109%	$197.4805	$197.48	$197.50	$197.50
Purchase #6	$198.87	12.165%	$223.0625	$223.06	$223.05	$223.10
Purchase #7	$50.59	3.458%	$52.3394	$52.34	$52.35	$52.30
7 purchase totals =	$992.15		$1,078.8816	$1,078.88	$1,078.90	$1,078.90