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	$155.50	10.669%	$172.0903	$172.09	$172.10	$172.10
Purchase #2	$70.63	11.208%	$78.5462	$78.55	$78.55	$78.50
Purchase #3	$206.35	7.447%	$221.7169	$221.72	$221.70	$221.70
Purchase #4	$104.39	6.802%	$111.4906	$111.49	$111.50	$111.50
Purchase #5	$173.44	3.523%	$179.5503	$179.55	$179.55	$179.60
Purchase #6	$196.77	11.120%	$218.6508	$218.65	$218.65	$218.70
Purchase #7	$90.84	12.345%	$102.0542	$102.05	$102.05	$102.10
7 purchase totals =	$997.92		$1,084.0993	$1,084.10	$1,084.10	$1,084.20