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	$90.32	4.592%	$94.4675	$94.47	$94.45	$94.50
Purchase #2	$33.77	4.665%	$35.3454	$35.35	$35.35	$35.30
Purchase #3	$204.35	4.147%	$212.8244	$212.82	$212.80	$212.80
Purchase #4	$118.29	4.572%	$123.6982	$123.70	$123.70	$123.70
Purchase #5	$97.39	6.351%	$103.5752	$103.58	$103.60	$103.60
Purchase #6	$51.64	7.625%	$55.5776	$55.58	$55.60	$55.60
Purchase #7	$126.59	10.222%	$139.53	$139.53	$139.55	$139.50
7 purchase totals =	$722.35		$765.0183	$765.03	$765.05	$765.00