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	$61.74	6.300%	$65.6296	$65.63	$65.65	$65.60
Purchase #2	$221.72	3.221%	$228.8616	$228.86	$228.85	$228.90
Purchase #3	$150.76	4.846%	$158.0658	$158.07	$158.05	$158.10
Purchase #4	$152.76	10.591%	$168.9388	$168.94	$168.95	$168.90
Purchase #5	$126.73	10.825%	$140.4485	$140.45	$140.45	$140.40
Purchase #6	$92.25	8.487%	$100.0793	$100.08	$100.10	$100.10
Purchase #7	$68.43	11.735%	$76.4603	$76.46	$76.45	$76.50
7 purchase totals =	$874.39		$938.4839	$938.49	$938.50	$938.50