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	$56.25	9.691%	$61.7012	$61.70	$61.70	$61.70
Purchase #2	$101.43	10.344%	$111.9219	$111.92	$111.90	$111.90
Purchase #3	$29.64	3.434%	$30.6578	$30.66	$30.65	$30.70
Purchase #4	$120.36	9.381%	$131.651	$131.65	$131.65	$131.70
Purchase #5	$34.64	12.123%	$38.8394	$38.84	$38.85	$38.80
Purchase #6	$212.55	7.250%	$227.9599	$227.96	$227.95	$228.00
Purchase #7	$100.90	8.349%	$109.3241	$109.32	$109.30	$109.30
7 purchase totals =	$655.77		$712.0553	$712.05	$712.00	$712.10