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	$138.75	10.726%	$153.6323	$153.63	$153.65	$153.60
Purchase #2	$109.86	9.720%	$120.5384	$120.54	$120.55	$120.50
Purchase #3	$64.94	3.478%	$67.1986	$67.20	$67.20	$67.20
Purchase #4	$30.76	9.576%	$33.7056	$33.71	$33.70	$33.70
Purchase #5	$109.82	9.142%	$119.8597	$119.86	$119.85	$119.90
Purchase #6	$99.50	10.618%	$110.0649	$110.06	$110.05	$110.10
Purchase #7	$123.28	6.614%	$131.4337	$131.43	$131.45	$131.40
7 purchase totals =	$676.91		$736.4332	$736.43	$736.45	$736.40