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	$60.31	9.195%	$65.8555	$65.86	$65.85	$65.90
Purchase #2	$187.71	9.498%	$205.5387	$205.54	$205.55	$205.50
Purchase #3	$31.89	12.319%	$35.8185	$35.82	$35.80	$35.80
Purchase #4	$35.62	8.356%	$38.5964	$38.60	$38.60	$38.60
Purchase #5	$67.27	7.170%	$72.0933	$72.09	$72.10	$72.10
Purchase #6	$163.63	6.619%	$174.4607	$174.46	$174.45	$174.50
Purchase #7	$58.74	13.722%	$66.8003	$66.80	$66.80	$66.80
7 purchase totals =	$605.17		$659.1634	$659.17	$659.15	$659.20