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	$103.86	8.118%	$112.2914	$112.29	$112.30	$112.30
Purchase #2	$224.31	8.179%	$242.6563	$242.66	$242.65	$242.70
Purchase #3	$96.59	12.618%	$108.7777	$108.78	$108.80	$108.80
Purchase #4	$53.64	10.438%	$59.2389	$59.24	$59.25	$59.20
Purchase #5	$23.95	4.512%	$25.0306	$25.03	$25.05	$25.00
Purchase #6	$49.40	13.519%	$56.0784	$56.08	$56.10	$56.10
Purchase #7	$155.60	5.704%	$164.4754	$164.48	$164.50	$164.50
7 purchase totals =	$707.35		$768.5487	$768.56	$768.65	$768.60