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	$207.25	7.179%	$222.1285	$222.13	$222.15	$222.10
Purchase #2	$230.34	4.576%	$240.8804	$240.88	$240.90	$240.90
Purchase #3	$34.76	4.676%	$36.3854	$36.39	$36.40	$36.40
Purchase #4	$243.64	4.588%	$254.8182	$254.82	$254.80	$254.80
Purchase #5	$100.39	10.646%	$111.0775	$111.08	$111.10	$111.10
Purchase #6	$138.87	3.386%	$143.5721	$143.57	$143.55	$143.60
Purchase #7	$176.81	7.618%	$190.2794	$190.28	$190.30	$190.30
7 purchase totals =	$1,132.06		$1,199.1415	$1,199.15	$1,199.20	$1,199.20