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	$202.31	4.834%	$212.0897	$212.09	$212.10	$212.10
Purchase #2	$126.78	4.722%	$132.7666	$132.77	$132.75	$132.80
Purchase #3	$127.76	10.789%	$141.544	$141.54	$141.55	$141.50
Purchase #4	$120.90	5.471%	$127.5144	$127.51	$127.50	$127.50
Purchase #5	$178.40	10.431%	$197.0089	$197.01	$197.00	$197.00
Purchase #6	$131.35	12.369%	$147.5967	$147.60	$147.60	$147.60
Purchase #7	$13.70	9.582%	$15.0127	$15.01	$15.00	$15.00
7 purchase totals =	$901.20		$973.5330	$973.53	$973.50	$973.50