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	$124.42	5.665%	$131.4684	$131.47	$131.45	$131.50
Purchase #2	$158.90	3.668%	$164.7285	$164.73	$164.75	$164.70
Purchase #3	$243.62	4.606%	$254.8411	$254.84	$254.85	$254.80
Purchase #4	$165.68	9.509%	$181.4345	$181.43	$181.45	$181.40
Purchase #5	$207.59	13.669%	$235.9655	$235.97	$235.95	$236.00
Purchase #6	$81.74	11.161%	$90.863	$90.86	$90.85	$90.90
Purchase #7	$209.74	3.172%	$216.393	$216.39	$216.40	$216.40
7 purchase totals =	$1,191.69		$1,275.6940	$1,275.69	$1,275.70	$1,275.70