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	$242.43	5.577%	$255.9503	$255.95	$255.95	$256.00
Purchase #2	$162.37	13.684%	$184.5887	$184.59	$184.60	$184.60
Purchase #3	$148.83	13.366%	$168.7226	$168.72	$168.70	$168.70
Purchase #4	$152.90	12.420%	$171.8902	$171.89	$171.90	$171.90
Purchase #5	$121.37	4.835%	$127.2382	$127.24	$127.25	$127.20
Purchase #6	$180.49	5.857%	$191.0613	$191.06	$191.05	$191.10
Purchase #7	$179.28	10.219%	$197.6006	$197.60	$197.60	$197.60
7 purchase totals =	$1,187.67		$1,297.0519	$1,297.05	$1,297.05	$1,297.10