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	$222.86	4.823%	$233.6085	$233.61	$233.60	$233.60
Purchase #2	$112.28	13.713%	$127.677	$127.68	$127.70	$127.70
Purchase #3	$192.69	7.224%	$206.6099	$206.61	$206.60	$206.60
Purchase #4	$91.60	7.838%	$98.7796	$98.78	$98.80	$98.80
Purchase #5	$74.68	13.272%	$84.5915	$84.59	$84.60	$84.60
Purchase #6	$46.59	12.644%	$52.4808	$52.48	$52.50	$52.50
Purchase #7	$150.28	9.458%	$164.4935	$164.49	$164.50	$164.50
7 purchase totals =	$890.98		$968.2408	$968.24	$968.30	$968.30