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	$147.52	11.554%	$164.5645	$164.56	$164.55	$164.60
Purchase #2	$76.97	11.307%	$85.673	$85.67	$85.65	$85.70
Purchase #3	$150.95	3.416%	$156.1065	$156.11	$156.10	$156.10
Purchase #4	$103.71	13.369%	$117.575	$117.58	$117.60	$117.60
Purchase #5	$42.39	3.709%	$43.9622	$43.96	$43.95	$44.00
Purchase #6	$109.65	6.459%	$116.7323	$116.73	$116.75	$116.70
Purchase #7	$51.31	10.370%	$56.6308	$56.63	$56.65	$56.60
7 purchase totals =	$682.50		$741.2443	$741.24	$741.25	$741.30