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	$154.36	6.776%	$164.8194	$164.82	$164.80	$164.80
Purchase #2	$204.92	4.728%	$214.6086	$214.61	$214.60	$214.60
Purchase #3	$19.55	9.481%	$21.4035	$21.40	$21.40	$21.40
Purchase #4	$171.99	5.429%	$181.3273	$181.33	$181.35	$181.30
Purchase #5	$218.35	4.231%	$227.5884	$227.59	$227.60	$227.60
Purchase #6	$153.89	9.371%	$168.311	$168.31	$168.30	$168.30
Purchase #7	$107.65	7.293%	$115.5009	$115.50	$115.50	$115.50
7 purchase totals =	$1,030.71		$1,093.5591	$1,093.56	$1,093.55	$1,093.50