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	$29.57	9.487%	$32.3753	$32.38	$32.40	$32.40
Purchase #2	$7.96	3.104%	$8.2071	$8.21	$8.20	$8.20
Purchase #3	$61.41	7.851%	$66.2313	$66.23	$66.25	$66.20
Purchase #4	$57.46	3.553%	$59.5016	$59.50	$59.50	$59.50
Purchase #5	$146.28	3.750%	$151.7655	$151.77	$151.75	$151.80
Purchase #6	$160.52	4.857%	$168.3165	$168.32	$168.30	$168.30
Purchase #7	$170.51	12.167%	$191.256	$191.26	$191.25	$191.30
7 purchase totals =	$633.71		$677.6533	$677.67	$677.65	$677.70