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	$176.54	8.443%	$191.4453	$191.45	$191.45	$191.40
Purchase #2	$185.67	13.190%	$210.1599	$210.16	$210.15	$210.20
Purchase #3	$248.63	9.356%	$271.8918	$271.89	$271.90	$271.90
Purchase #4	$82.82	5.241%	$87.1606	$87.16	$87.15	$87.20
Purchase #5	$101.54	12.731%	$114.4671	$114.47	$114.45	$114.50
Purchase #6	$148.86	7.643%	$160.2374	$160.24	$160.25	$160.20
Purchase #7	$137.32	4.204%	$143.0929	$143.09	$143.10	$143.10
7 purchase totals =	$1,081.38		$1,178.4550	$1,178.46	$1,178.45	$1,178.50