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	$172.88	3.752%	$179.3665	$179.37	$179.35	$179.40
Purchase #2	$70.72	10.766%	$78.3337	$78.33	$78.35	$78.30
Purchase #3	$15.31	12.825%	$17.2735	$17.27	$17.25	$17.30
Purchase #4	$108.97	3.836%	$113.1501	$113.15	$113.15	$113.20
Purchase #5	$187.69	12.347%	$210.8641	$210.86	$210.85	$210.90
Purchase #6	$60.78	10.118%	$66.9297	$66.93	$66.95	$66.90
Purchase #7	$91.64	3.746%	$95.0728	$95.07	$95.05	$95.10
7 purchase totals =	$707.99		$760.9904	$760.98	$760.95	$761.10