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	$61.66	3.652%	$63.9118	$63.91	$63.90	$63.90
Purchase #2	$85.60	5.783%	$90.5502	$90.55	$90.55	$90.60
Purchase #3	$25.73	5.107%	$27.044	$27.04	$27.05	$27.00
Purchase #4	$62.68	4.169%	$65.2931	$65.29	$65.30	$65.30
Purchase #5	$243.30	9.579%	$266.6057	$266.61	$266.60	$266.60
Purchase #6	$68.59	3.202%	$70.7863	$70.79	$70.80	$70.80
Purchase #7	$110.29	5.417%	$116.2644	$116.26	$116.25	$116.30
7 purchase totals =	$657.85		$700.4555	$700.45	$700.45	$700.50