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	$194.54	7.269%	$208.6811	$208.68	$208.70	$208.70
Purchase #2	$156.83	13.798%	$178.4694	$178.47	$178.45	$178.50
Purchase #3	$84.72	6.201%	$89.9735	$89.97	$89.95	$90.00
Purchase #4	$98.48	3.354%	$101.783	$101.78	$101.80	$101.80
Purchase #5	$169.99	10.495%	$187.8305	$187.83	$187.85	$187.80
Purchase #6	$232.32	9.152%	$253.5819	$253.58	$253.60	$253.60
Purchase #7	$32.93	12.683%	$37.1065	$37.11	$37.10	$37.10
7 purchase totals =	$969.81		$1,057.4259	$1,057.42	$1,057.45	$1,057.50