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	$90.83	11.138%	$100.9466	$100.95	$100.95	$100.90
Purchase #2	$53.91	10.758%	$59.7096	$59.71	$59.70	$59.70
Purchase #3	$158.31	5.870%	$167.6028	$167.60	$167.60	$167.60
Purchase #4	$70.85	10.749%	$78.4657	$78.47	$78.45	$78.50
Purchase #5	$202.33	12.281%	$227.1781	$227.18	$227.20	$227.20
Purchase #6	$51.83	7.293%	$55.61	$55.61	$55.60	$55.60
Purchase #7	$114.73	10.467%	$126.7388	$126.74	$126.75	$126.70
7 purchase totals =	$742.79		$816.2516	$816.26	$816.25	$816.20