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	$34.64	4.583%	$36.2276	$36.23	$36.25	$36.20
Purchase #2	$168.63	13.665%	$191.6733	$191.67	$191.65	$191.70
Purchase #3	$56.58	5.808%	$59.8662	$59.87	$59.85	$59.90
Purchase #4	$110.70	8.755%	$120.3918	$120.39	$120.40	$120.40
Purchase #5	$95.83	13.850%	$109.1025	$109.10	$109.10	$109.10
Purchase #6	$48.71	4.259%	$50.7846	$50.78	$50.80	$50.80
Purchase #7	$178.25	5.580%	$188.1964	$188.20	$188.20	$188.20
7 purchase totals =	$693.34		$756.2424	$756.24	$756.25	$756.30