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	$241.76	6.118%	$256.5509	$256.55	$256.55	$256.60
Purchase #2	$150.47	13.695%	$171.0769	$171.08	$171.10	$171.10
Purchase #3	$74.78	5.570%	$78.9452	$78.95	$78.95	$78.90
Purchase #4	$84.92	5.384%	$89.4921	$89.49	$89.50	$89.50
Purchase #5	$161.98	13.427%	$183.7291	$183.73	$183.75	$183.70
Purchase #6	$228.88	10.411%	$252.7087	$252.71	$252.70	$252.70
Purchase #7	$184.90	13.359%	$209.6008	$209.60	$209.60	$209.60
7 purchase totals =	$1,127.69		$1,242.1037	$1,242.11	$1,242.15	$1,242.10