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	$131.46	7.801%	$141.7152	$141.72	$141.70	$141.70
Purchase #2	$114.86	10.154%	$126.5229	$126.52	$126.50	$126.50
Purchase #3	$158.41	12.160%	$177.6727	$177.67	$177.65	$177.70
Purchase #4	$123.36	11.509%	$137.5575	$137.56	$137.55	$137.60
Purchase #5	$103.82	9.372%	$113.55	$113.55	$113.55	$113.60
Purchase #6	$99.42	12.107%	$111.4568	$111.46	$111.45	$111.50
Purchase #7	$152.85	7.380%	$164.1303	$164.13	$164.15	$164.10
7 purchase totals =	$884.18		$972.6054	$972.61	$972.55	$972.70