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	$191.40	4.228%	$199.4924	$199.49	$199.50	$199.50
Purchase #2	$106.84	6.546%	$113.8337	$113.83	$113.85	$113.80
Purchase #3	$97.36	6.221%	$103.4168	$103.42	$103.40	$103.40
Purchase #4	$42.63	10.713%	$47.197	$47.20	$47.20	$47.20
Purchase #5	$124.96	3.627%	$129.4923	$129.49	$129.50	$129.50
Purchase #6	$60.89	9.177%	$66.4779	$66.48	$66.50	$66.50
Purchase #7	$29.53	13.381%	$33.4814	$33.48	$33.50	$33.50
7 purchase totals =	$653.61		$693.3915	$693.39	$693.45	$693.40