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	$162.53	10.691%	$179.9061	$179.91	$179.90	$179.90
Purchase #2	$151.98	3.224%	$156.8798	$156.88	$156.90	$156.90
Purchase #3	$137.49	13.670%	$156.2849	$156.28	$156.30	$156.30
Purchase #4	$27.83	5.188%	$29.2738	$29.27	$29.25	$29.30
Purchase #5	$192.39	4.457%	$200.9648	$200.96	$200.95	$201.00
Purchase #6	$76.90	11.548%	$85.7804	$85.78	$85.80	$85.80
Purchase #7	$171.85	10.809%	$190.4253	$190.43	$190.45	$190.40
7 purchase totals =	$920.97		$999.5151	$999.51	$999.55	$999.60