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	$164.50	11.156%	$182.8516	$182.85	$182.85	$182.90
Purchase #2	$140.76	7.323%	$151.0679	$151.07	$151.05	$151.10
Purchase #3	$86.35	4.284%	$90.0492	$90.05	$90.05	$90.00
Purchase #4	$241.80	8.246%	$261.7388	$261.74	$261.75	$261.70
Purchase #5	$211.81	12.156%	$237.5576	$237.56	$237.55	$237.60
Purchase #6	$159.58	3.116%	$164.5525	$164.55	$164.55	$164.60
Purchase #7	$182.98	4.519%	$191.2489	$191.25	$191.25	$191.20
7 purchase totals =	$1,187.78		$1,279.0665	$1,279.07	$1,279.05	$1,279.10