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	$61.53	11.635%	$68.689	$68.69	$68.70	$68.70
Purchase #2	$202.65	7.777%	$218.4101	$218.41	$218.40	$218.40
Purchase #3	$13.38	10.353%	$14.7652	$14.77	$14.75	$14.80
Purchase #4	$89.35	12.184%	$100.2364	$100.24	$100.25	$100.20
Purchase #5	$35.42	5.769%	$37.4634	$37.46	$37.45	$37.50
Purchase #6	$235.83	12.534%	$265.3889	$265.39	$265.40	$265.40
Purchase #7	$82.37	7.504%	$88.551	$88.55	$88.55	$88.60
7 purchase totals =	$720.53		$793.5040	$793.51	$793.50	$793.60