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	$48.95	13.840%	$55.7247	$55.72	$55.70	$55.70
Purchase #2	$12.83	12.313%	$14.4098	$14.41	$14.40	$14.40
Purchase #3	$167.59	10.286%	$184.8283	$184.83	$184.85	$184.80
Purchase #4	$216.61	10.304%	$238.9295	$238.93	$238.95	$238.90
Purchase #5	$100.45	9.405%	$109.8973	$109.90	$109.90	$109.90
Purchase #6	$237.69	3.176%	$245.239	$245.24	$245.25	$245.20
Purchase #7	$121.72	8.183%	$131.6803	$131.68	$131.70	$131.70
7 purchase totals =	$905.84		$980.7089	$980.71	$980.75	$980.60