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	$95.76	10.319%	$105.6415	$105.64	$105.65	$105.60
Purchase #2	$171.72	6.539%	$182.9488	$182.95	$182.95	$182.90
Purchase #3	$181.92	8.688%	$197.7252	$197.73	$197.75	$197.70
Purchase #4	$59.75	11.629%	$66.6983	$66.70	$66.70	$66.70
Purchase #5	$157.83	9.108%	$172.2052	$172.21	$172.20	$172.20
Purchase #6	$226.31	3.140%	$233.4161	$233.42	$233.40	$233.40
Purchase #7	$67.84	7.403%	$72.8622	$72.86	$72.85	$72.90
7 purchase totals =	$961.13		$1,031.4973	$1,031.51	$1,031.50	$1,031.40