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	$153.91	6.856%	$164.4621	$164.46	$164.45	$164.50
Purchase #2	$28.55	8.834%	$31.0721	$31.07	$31.05	$31.10
Purchase #3	$46.38	10.756%	$51.3686	$51.37	$51.35	$51.40
Purchase #4	$248.76	5.513%	$262.4741	$262.47	$262.45	$262.50
Purchase #5	$128.32	9.776%	$140.8646	$140.86	$140.85	$140.90
Purchase #6	$100.54	4.376%	$104.9396	$104.94	$104.95	$104.90
Purchase #7	$56.32	7.331%	$60.4488	$60.45	$60.45	$60.40
7 purchase totals =	$762.78		$815.6299	$815.62	$815.55	$815.70