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	$32.51	9.694%	$35.6615	$35.66	$35.65	$35.70
Purchase #2	$83.39	8.489%	$90.469	$90.47	$90.45	$90.50
Purchase #3	$151.64	12.450%	$170.5192	$170.52	$170.50	$170.50
Purchase #4	$208.27	3.352%	$215.2512	$215.25	$215.25	$215.30
Purchase #5	$49.56	5.209%	$52.1416	$52.14	$52.15	$52.10
Purchase #6	$116.60	3.369%	$120.5283	$120.53	$120.55	$120.50
Purchase #7	$75.64	8.530%	$82.0921	$82.09	$82.10	$82.10
7 purchase totals =	$717.61		$766.6629	$766.66	$766.65	$766.70