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	$144.97	9.329%	$158.4943	$158.49	$158.50	$158.50
Purchase #2	$161.96	13.216%	$183.3646	$183.36	$183.35	$183.40
Purchase #3	$101.60	3.659%	$105.3175	$105.32	$105.30	$105.30
Purchase #4	$126.83	12.524%	$142.7142	$142.71	$142.70	$142.70
Purchase #5	$153.26	12.446%	$172.3347	$172.33	$172.35	$172.30
Purchase #6	$118.45	10.697%	$131.1206	$131.12	$131.10	$131.10
Purchase #7	$57.77	3.837%	$59.9866	$59.99	$60.00	$60.00
7 purchase totals =	$864.84		$953.3325	$953.32	$953.30	$953.30