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	$90.75	4.725%	$95.0379	$95.04	$95.05	$95.00
Purchase #2	$98.45	11.115%	$109.3927	$109.39	$109.40	$109.40
Purchase #3	$132.78	9.873%	$145.8894	$145.89	$145.90	$145.90
Purchase #4	$94.45	12.486%	$106.243	$106.24	$106.25	$106.20
Purchase #5	$31.64	9.230%	$34.5604	$34.56	$34.55	$34.60
Purchase #6	$37.91	5.629%	$40.044	$40.04	$40.05	$40.00
Purchase #7	$103.55	5.627%	$109.3768	$109.38	$109.40	$109.40
7 purchase totals =	$589.53		$640.5442	$640.54	$640.60	$640.50