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	$241.75	11.807%	$270.2934	$270.29	$270.30	$270.30
Purchase #2	$242.98	10.349%	$268.126	$268.13	$268.15	$268.10
Purchase #3	$222.60	3.531%	$230.46	$230.46	$230.45	$230.50
Purchase #4	$47.88	10.487%	$52.9012	$52.90	$52.90	$52.90
Purchase #5	$40.41	8.625%	$43.8954	$43.90	$43.90	$43.90
Purchase #6	$42.60	8.736%	$46.3215	$46.32	$46.30	$46.30
Purchase #7	$224.73	7.854%	$242.3803	$242.38	$242.40	$242.40
7 purchase totals =	$1,062.95		$1,154.3778	$1,154.38	$1,154.40	$1,154.40