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	$242.89	13.485%	$275.6437	$275.64	$275.65	$275.60
Purchase #2	$51.70	12.509%	$58.1672	$58.17	$58.15	$58.20
Purchase #3	$141.71	11.365%	$157.8153	$157.82	$157.80	$157.80
Purchase #4	$160.61	9.788%	$176.3305	$176.33	$176.35	$176.30
Purchase #5	$56.37	9.838%	$61.9157	$61.92	$61.90	$61.90
Purchase #6	$173.99	13.154%	$196.8766	$196.88	$196.90	$196.90
Purchase #7	$184.73	12.699%	$208.1889	$208.19	$208.20	$208.20
7 purchase totals =	$1,012.00		$1,134.9379	$1,134.95	$1,134.95	$1,134.90