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	$173.32	4.791%	$181.6238	$181.62	$181.60	$181.60
Purchase #2	$171.67	6.365%	$182.5968	$182.60	$182.60	$182.60
Purchase #3	$29.48	6.301%	$31.3375	$31.34	$31.35	$31.30
Purchase #4	$151.71	13.221%	$171.7676	$171.77	$171.75	$171.80
Purchase #5	$146.70	13.470%	$166.4605	$166.46	$166.45	$166.50
Purchase #6	$121.47	5.173%	$127.7536	$127.75	$127.75	$127.80
Purchase #7	$68.40	6.688%	$72.9746	$72.97	$72.95	$73.00
7 purchase totals =	$862.75		$934.5144	$934.51	$934.45	$934.60