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	$112.43	10.300%	$124.0103	$124.01	$124.00	$124.00
Purchase #2	$40.30	3.779%	$41.8229	$41.82	$41.80	$41.80
Purchase #3	$212.99	13.435%	$241.6052	$241.61	$241.60	$241.60
Purchase #4	$71.59	9.470%	$78.3696	$78.37	$78.35	$78.40
Purchase #5	$223.81	5.843%	$236.8872	$236.89	$236.90	$236.90
Purchase #6	$161.59	13.299%	$183.0799	$183.08	$183.10	$183.10
Purchase #7	$125.91	13.689%	$143.1458	$143.15	$143.15	$143.10
7 purchase totals =	$948.62		$1,048.9209	$1,048.93	$1,048.90	$1,048.90