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	$156.81	9.360%	$171.4874	$171.49	$171.50	$171.50
Purchase #2	$232.86	9.244%	$254.3856	$254.39	$254.40	$254.40
Purchase #3	$135.40	4.783%	$141.8762	$141.88	$141.90	$141.90
Purchase #4	$115.89	7.156%	$124.1831	$124.18	$124.20	$124.20
Purchase #5	$77.42	13.295%	$87.713	$87.71	$87.70	$87.70
Purchase #6	$182.59	12.412%	$205.2531	$205.25	$205.25	$205.30
Purchase #7	$89.92	8.439%	$97.5083	$97.51	$97.50	$97.50
7 purchase totals =	$990.89		$1,082.4067	$1,082.41	$1,082.45	$1,082.50