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	$151.42	8.720%	$164.6238	$164.62	$164.60	$164.60
Purchase #2	$33.99	13.704%	$38.648	$38.65	$38.65	$38.60
Purchase #3	$54.25	12.858%	$61.2255	$61.23	$61.25	$61.20
Purchase #4	$22.31	4.474%	$23.3081	$23.31	$23.30	$23.30
Purchase #5	$40.70	13.781%	$46.3089	$46.31	$46.30	$46.30
Purchase #6	$248.57	3.229%	$256.5963	$256.60	$256.60	$256.60
Purchase #7	$44.45	12.506%	$50.0089	$50.01	$50.00	$50.00
7 purchase totals =	$595.69		$640.7195	$640.73	$640.70	$640.60