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	$60.95	10.592%	$67.4058	$67.41	$67.40	$67.40
Purchase #2	$84.55	5.520%	$89.2172	$89.22	$89.20	$89.20
Purchase #3	$240.35	5.793%	$254.2735	$254.27	$254.25	$254.30
Purchase #4	$111.47	7.116%	$119.4022	$119.40	$119.40	$119.40
Purchase #5	$233.78	3.728%	$242.4953	$242.50	$242.50	$242.50
Purchase #6	$52.96	13.278%	$59.992	$59.99	$60.00	$60.00
Purchase #7	$151.84	13.832%	$172.8425	$172.84	$172.85	$172.80
7 purchase totals =	$935.90		$1,005.6285	$1,005.63	$1,005.60	$1,005.60