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	$171.25	3.342%	$176.9732	$176.97	$176.95	$177.00
Purchase #2	$183.89	11.540%	$205.1109	$205.11	$205.10	$205.10
Purchase #3	$55.84	10.417%	$61.6569	$61.66	$61.65	$61.70
Purchase #4	$38.47	6.254%	$40.8759	$40.88	$40.90	$40.90
Purchase #5	$65.51	9.426%	$71.685	$71.69	$71.70	$71.70
Purchase #6	$214.59	9.872%	$235.7743	$235.77	$235.75	$235.80
Purchase #7	$126.70	11.136%	$140.8093	$140.81	$140.80	$140.80
7 purchase totals =	$856.25		$932.8855	$932.89	$932.85	$933.00