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	$73.30	7.436%	$78.7506	$78.75	$78.75	$78.80
Purchase #2	$146.72	4.140%	$152.7942	$152.79	$152.80	$152.80
Purchase #3	$226.99	13.379%	$257.359	$257.36	$257.35	$257.40
Purchase #4	$119.97	5.426%	$126.4796	$126.48	$126.50	$126.50
Purchase #5	$248.46	5.566%	$262.2893	$262.29	$262.30	$262.30
Purchase #6	$133.69	13.335%	$151.5176	$151.52	$151.50	$151.50
Purchase #7	$55.43	5.244%	$58.3367	$58.34	$58.35	$58.30
7 purchase totals =	$1,004.56		$1,087.5270	$1,087.53	$1,087.55	$1,087.60