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	$57.39	12.524%	$64.5775	$64.58	$64.60	$64.60
Purchase #2	$153.98	5.385%	$162.2718	$162.27	$162.25	$162.30
Purchase #3	$13.59	6.543%	$14.4792	$14.48	$14.50	$14.50
Purchase #4	$48.73	9.137%	$53.1825	$53.18	$53.20	$53.20
Purchase #5	$37.26	12.325%	$41.8523	$41.85	$41.85	$41.90
Purchase #6	$59.94	12.421%	$67.3851	$67.39	$67.40	$67.40
Purchase #7	$224.54	11.207%	$249.7042	$249.70	$249.70	$249.70
7 purchase totals =	$595.43		$653.4526	$653.45	$653.50	$653.60