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	$165.64	10.386%	$182.8434	$182.84	$182.85	$182.80
Purchase #2	$101.48	5.529%	$107.0908	$107.09	$107.10	$107.10
Purchase #3	$199.64	7.622%	$214.8566	$214.86	$214.85	$214.90
Purchase #4	$120.65	5.659%	$127.4776	$127.48	$127.50	$127.50
Purchase #5	$110.50	7.801%	$119.1201	$119.12	$119.10	$119.10
Purchase #6	$165.76	10.230%	$182.7172	$182.72	$182.70	$182.70
Purchase #7	$133.71	9.568%	$146.5034	$146.50	$146.50	$146.50
7 purchase totals =	$997.38		$1,080.6091	$1,080.61	$1,080.60	$1,080.60