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	$183.69	11.786%	$205.3397	$205.34	$205.35	$205.30
Purchase #2	$68.61	7.718%	$73.9053	$73.91	$73.90	$73.90
Purchase #3	$36.84	4.177%	$38.3788	$38.38	$38.40	$38.40
Purchase #4	$233.74	9.300%	$255.4778	$255.48	$255.50	$255.50
Purchase #5	$13.85	4.544%	$14.4793	$14.48	$14.50	$14.50
Purchase #6	$122.64	11.260%	$136.4493	$136.45	$136.45	$136.40
Purchase #7	$59.93	9.410%	$65.5694	$65.57	$65.55	$65.60
7 purchase totals =	$719.30		$789.5996	$789.61	$789.65	$789.60