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	$159.85	10.648%	$176.8708	$176.87	$176.85	$176.90
Purchase #2	$100.69	8.762%	$109.5125	$109.51	$109.50	$109.50
Purchase #3	$94.67	6.198%	$100.5376	$100.54	$100.55	$100.50
Purchase #4	$97.29	12.525%	$109.4756	$109.48	$109.50	$109.50
Purchase #5	$65.98	7.418%	$70.8744	$70.87	$70.85	$70.90
Purchase #6	$7.82	7.226%	$8.3851	$8.39	$8.40	$8.40
Purchase #7	$162.78	9.570%	$178.358	$178.36	$178.35	$178.40
7 purchase totals =	$689.08		$754.0140	$754.02	$754.00	$754.10