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	$208.43	3.345%	$215.402	$215.40	$215.40	$215.40
Purchase #2	$58.93	5.727%	$62.3049	$62.30	$62.30	$62.30
Purchase #3	$64.54	4.513%	$67.4527	$67.45	$67.45	$67.50
Purchase #4	$34.41	8.304%	$37.2674	$37.27	$37.25	$37.30
Purchase #5	$28.39	12.226%	$31.861	$31.86	$31.85	$31.90
Purchase #6	$241.56	10.121%	$266.0083	$266.01	$266.00	$266.00
Purchase #7	$33.40	3.228%	$34.4782	$34.48	$34.50	$34.50
7 purchase totals =	$669.66		$714.7745	$714.77	$714.75	$714.90