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	$131.44	7.714%	$141.5793	$141.58	$141.60	$141.60
Purchase #2	$51.30	5.130%	$53.9317	$53.93	$53.95	$53.90
Purchase #3	$73.25	7.689%	$78.8822	$78.88	$78.90	$78.90
Purchase #4	$181.89	5.808%	$192.4542	$192.45	$192.45	$192.50
Purchase #5	$84.43	9.822%	$92.7227	$92.72	$92.70	$92.70
Purchase #6	$169.79	12.282%	$190.6436	$190.64	$190.65	$190.60
Purchase #7	$166.99	7.758%	$179.9451	$179.95	$179.95	$179.90
7 purchase totals =	$859.09		$930.1588	$930.15	$930.20	$930.10