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	$62.60	3.797%	$64.9769	$64.98	$65.00	$65.00
Purchase #2	$143.90	8.461%	$156.0754	$156.08	$156.10	$156.10
Purchase #3	$100.76	8.670%	$109.4959	$109.50	$109.50	$109.50
Purchase #4	$31.70	6.799%	$33.8553	$33.86	$33.85	$33.90
Purchase #5	$163.58	4.485%	$170.9166	$170.92	$170.90	$170.90
Purchase #6	$92.63	10.767%	$102.6035	$102.60	$102.60	$102.60
Purchase #7	$93.29	13.478%	$105.8636	$105.86	$105.85	$105.90
7 purchase totals =	$688.46		$743.7872	$743.80	$743.80	$743.90