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	$77.61	10.412%	$85.6908	$85.69	$85.70	$85.70
Purchase #2	$100.86	5.761%	$106.6705	$106.67	$106.65	$106.70
Purchase #3	$155.54	5.817%	$164.5878	$164.59	$164.60	$164.60
Purchase #4	$128.80	5.829%	$136.3078	$136.31	$136.30	$136.30
Purchase #5	$239.84	12.774%	$270.4772	$270.48	$270.50	$270.50
Purchase #6	$13.93	8.307%	$15.0872	$15.09	$15.10	$15.10
Purchase #7	$139.64	3.443%	$144.4478	$144.45	$144.45	$144.40
7 purchase totals =	$856.22		$923.2691	$923.28	$923.30	$923.30