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	$9.84	7.526%	$10.5806	$10.58	$10.60	$10.60
Purchase #2	$36.42	4.481%	$38.052	$38.05	$38.05	$38.10
Purchase #3	$208.62	4.166%	$217.3111	$217.31	$217.30	$217.30
Purchase #4	$215.73	11.673%	$240.9122	$240.91	$240.90	$240.90
Purchase #5	$79.39	4.670%	$83.0975	$83.10	$83.10	$83.10
Purchase #6	$200.63	11.437%	$223.5761	$223.58	$223.60	$223.60
Purchase #7	$134.54	12.576%	$151.4598	$151.46	$151.45	$151.50
7 purchase totals =	$885.17		$964.9893	$964.99	$965.00	$965.10