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	$160.54	7.407%	$172.4312	$172.43	$172.45	$172.40
Purchase #2	$164.74	12.727%	$185.7065	$185.71	$185.70	$185.70
Purchase #3	$68.26	3.177%	$70.4286	$70.43	$70.45	$70.40
Purchase #4	$202.59	9.841%	$222.5269	$222.53	$222.55	$222.50
Purchase #5	$194.77	12.688%	$219.4824	$219.48	$219.50	$219.50
Purchase #6	$56.61	10.873%	$62.7652	$62.77	$62.75	$62.80
Purchase #7	$205.31	7.803%	$221.3303	$221.33	$221.35	$221.30
7 purchase totals =	$1,052.82		$1,154.6711	$1,154.68	$1,154.75	$1,154.60