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	$220.73	7.455%	$237.1854	$237.19	$237.20	$237.20
Purchase #2	$127.83	13.141%	$144.6281	$144.63	$144.65	$144.60
Purchase #3	$161.27	12.546%	$181.5029	$181.50	$181.50	$181.50
Purchase #4	$105.64	5.686%	$111.6467	$111.65	$111.65	$111.60
Purchase #5	$126.61	8.459%	$137.3199	$137.32	$137.30	$137.30
Purchase #6	$136.40	10.258%	$150.3919	$150.39	$150.40	$150.40
Purchase #7	$126.72	13.535%	$143.8716	$143.87	$143.85	$143.90
7 purchase totals =	$1,005.20		$1,106.5465	$1,106.55	$1,106.55	$1,106.50