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	$228.56	4.406%	$238.6304	$238.63	$238.65	$238.60
Purchase #2	$197.32	10.304%	$217.6519	$217.65	$217.65	$217.70
Purchase #3	$82.78	8.673%	$89.9595	$89.96	$89.95	$90.00
Purchase #4	$236.42	8.463%	$256.4282	$256.43	$256.45	$256.40
Purchase #5	$227.34	3.624%	$235.5788	$235.58	$235.60	$235.60
Purchase #6	$250.30	12.238%	$280.9317	$280.93	$280.95	$280.90
Purchase #7	$135.52	4.146%	$141.1387	$141.14	$141.15	$141.10
7 purchase totals =	$1,358.24		$1,460.3192	$1,460.32	$1,460.40	$1,460.30