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	$248.74	5.237%	$261.7665	$261.77	$261.75	$261.80
Purchase #2	$129.51	13.193%	$146.5963	$146.60	$146.60	$146.60
Purchase #3	$126.33	8.204%	$136.6941	$136.69	$136.70	$136.70
Purchase #4	$102.29	8.803%	$111.2946	$111.29	$111.30	$111.30
Purchase #5	$60.87	6.559%	$64.8625	$64.86	$64.85	$64.90
Purchase #6	$94.27	9.802%	$103.5103	$103.51	$103.50	$103.50
Purchase #7	$181.63	4.790%	$190.3301	$190.33	$190.35	$190.30
7 purchase totals =	$943.64		$1,015.0544	$1,015.05	$1,015.05	$1,015.10