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	$81.28	6.257%	$86.3657	$86.37	$86.35	$86.40
Purchase #2	$130.36	8.624%	$141.6022	$141.60	$141.60	$141.60
Purchase #3	$39.94	9.807%	$43.8569	$43.86	$43.85	$43.90
Purchase #4	$124.33	7.110%	$133.1699	$133.17	$133.15	$133.20
Purchase #5	$72.93	8.249%	$78.946	$78.95	$78.95	$78.90
Purchase #6	$162.93	6.419%	$173.3885	$173.39	$173.40	$173.40
Purchase #7	$179.63	10.716%	$198.8792	$198.88	$198.90	$198.90
7 purchase totals =	$791.40		$856.2084	$856.22	$856.20	$856.30