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	$54.30	11.210%	$60.387	$60.39	$60.40	$60.40
Purchase #2	$97.61	12.673%	$109.9801	$109.98	$110.00	$110.00
Purchase #3	$49.59	5.554%	$52.3442	$52.34	$52.35	$52.30
Purchase #4	$156.69	3.533%	$162.2259	$162.23	$162.25	$162.20
Purchase #5	$51.60	12.357%	$57.9762	$57.98	$58.00	$58.00
Purchase #6	$154.30	11.669%	$172.3053	$172.31	$172.30	$172.30
Purchase #7	$49.43	4.183%	$51.4977	$51.50	$51.50	$51.50
7 purchase totals =	$613.52		$666.7164	$666.73	$666.80	$666.70