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	$179.84	13.692%	$204.4637	$204.46	$204.45	$204.50
Purchase #2	$96.76	3.810%	$100.4466	$100.45	$100.45	$100.40
Purchase #3	$180.76	13.871%	$205.8332	$205.83	$205.85	$205.80
Purchase #4	$237.55	7.847%	$256.1905	$256.19	$256.20	$256.20
Purchase #5	$52.82	11.799%	$59.0522	$59.05	$59.05	$59.10
Purchase #6	$144.85	4.832%	$151.8492	$151.85	$151.85	$151.80
Purchase #7	$96.90	4.288%	$101.0551	$101.06	$101.05	$101.10
7 purchase totals =	$989.48		$1,078.8905	$1,078.89	$1,078.90	$1,078.90